The Medieval Inquisitions were a blessing.

I believe that Hell, a spiritual place and state of eternal torment and tortures, is absolutely real, just as every bit as real as the keyboard that I am typing on at this very moment and the very computer monitor that is displaying this text.  I accept the existence of Hell, as I accept the curvature of the Earth, that our planet is a round, ball-like object in space.  That the Earth is not a square, a cube, or a pancake is absolutely certain, and it is just as equally certain to say that when a human being dies physically that individual is forever judged to everlasting life or to everlasting death.  Many people, of course, do not believe this, but such does absolutely nothing in changing the fact that it is absolutely true.

The Medieval Catholics believed in the existence of Hell, and they believed that heresy, the choice to deny that which the One and Triune God had revealed to His Creation was a mortal sin.  The Apostle Paul was quite clear about this, stating,

"But though we, or an angel from heaven, preach a gospel to you besides that which we have preached to you, let him be anathema.  As we said before, so now I say again: If any one preach to you a gospel, besides that which you have received, let him be anathema." (Galatians 1:8-9)

Some translations of Sacred Scripture use the phrase "eternally condemned" in place of  "anathema."  Elsewhere, Saint Paul states,

"To deliver such a one to Satan for the destruction of the flesh, that the spirit may be saved in the day of our Lord Jesus Christ." (1 Corinthians 5:5)

"Of whom is Hymeneus and Alexander, whom I have delivered up to Satan, that they may learn not to blaspheme." (1 Timothy 1:20)

The Medievals took such verses literally and how could they not do so?  Our Lord said,

"And if thy right eye scandalize thee, pluck it out and cast it from thee. For it is expedient for thee that one of thy members should perish, rather than that thy whole body be cast into hell.  And if thy right hand scandalize thee, cut it off, and cast it from thee: for it is expedient for thee that one of thy members should perish, rather than that thy whole body be cast into hell." (Matthew 5:29-30)

Our Lords words are clear and straightforward:  Hell is real, therefore, avoid it at all costs.  However, before engaging in self-mutilation, I would suggest that you instead confess daily, that is, receive the Sacrament of Reconciliation on a daily basis if you are struggling with sin, or at least weekly.  You and your confessor can decide what to do if frequent confession is not assisting you in overcoming your sins.

Heresy is an excommunicable offense, even in the 1983 Code of Canon Law:

Can. 1364 §1. Without prejudice to the prescript of can. 194, §1, n. 2, an apostate from the faith, a heretic, or a schismatic incurs a latae sententiae excommunication; in addition, a cleric can be punished with the penalties mentioned in can. 1336, §1, nn. 1, 2, and 3.
§2. If contumacy of long duration or the gravity of scandal demands it, other penalties can be added, including dismissal from the clerical state.

Note that murder, rape, and molestation of young children are not excommunicable offenses.  Choosing to deny that which God, a Perfect Being, has revealed separates one from the Mystical Body of Jesus Christ, which is the Roman Catholic Church.  Saint Thomas was quite clear about society's right, duty, and obligation with respect to those individuals who obstinately and without repentance deny the Truth:

“With regard to heretics two points must be observed: one, on their own side; the other, on the side of the Church. On their own side there is the sin, whereby they deserve not only to be separated from the Church by excommunication, but also to be severed from the world by death. For it is a much graver matter to corrupt the faith which quickens the soul, than to forge money, which supports temporal life. Wherefore if forgers of money and other evil-doers are forthwith condemned to death by the secular authority, much more reason is there for heretics, as soon as they are convicted of heresy, to be not only excommunicated but even put to death.

On the part of the Church, however, there is mercy which looks to the conversion of the wanderer, wherefore she condemns not at once, but 'after the first and second admonition,' as the Apostle directs: after that, if he is yet stubborn, the Church no longer hoping for his conversion, looks to the salvation of others, by excommunicating him and separating him from the Church, and furthermore delivers him to the secular tribunal to be exterminated thereby from the world by death. For Jerome commenting on Gal. 5:9, 'A little leaven,' says: 'Cut off the decayed flesh, expel the mangy sheep from the fold, lest the whole house, the whole paste, the whole body, the whole flock, burn, perish, rot, die. Arius was but one spark in Alexandria, but as that spark was not at once put out, the whole earth was laid waste by its flame.'” (Summa Theologica, IIa IIae, q.11, a.3)

Strong words, to be sure, especially for a society where (at least in the Western World) belief in religious freedom is virtually ubiquitous.  However, does religious freedom make sense?

No, it does not.  As was proven long ago, God is a Perfect Being, therefore, what He desires and "believes in" is also perfect.  To say that God does not have perfect ideas and values is to say that He is not perfect, and to say that He does not have ideas and values would be to say that He is not God.  To obstinately deny that which God has revealed through Christ and His Church is, therefore, to commit sin, which is anything that is contrary to the Perfect goodness of God.  Since unbelief and/or a false profession of belief, as Saint Thomas has already taught us, is something that could send us to Hell forever, heresy is to the soul what murder is to the body.  Not only is the heretic jeopardizing his or her own salvation, but is threatening the salvation of others, by leading them into heresy and, perhaps, everlasting damnation.

Saint Thomas continues,

“According to Decret. (xxiv, qu. iii, can. Notandum), 'to be excommunicated is not to be uprooted.' A man is excommunicated, as the Apostle says (1 Cor. 5:5) that his 'spirit may be saved in the day of Our Lord.' Yet if heretics be altogether uprooted by death, this is not contrary to Our Lord’s command, which is to be understood as referring to the case when the cockle cannot be plucked up without plucking up the wheat, as we explained above (q. 10, a. 8, ad 1), when treating of unbelievers in general.” (Summa Theologica, IIa IIae, q.11, a.3, ad 3)

In God’s tribunal, those who return are always received, because God is a searcher of hearts, and knows those who return in sincerity. But the Church cannot imitate God in this, for she presumes that those who relapse after being once received, are not sincere in their return; hence she does not debar them from the way of salvation, but neither does she protect them from the sentence of death.” (Summa Theologica, IIa IIae, q.11, a.4, ad 1)

The Medievals, in embracing (which means defending) the Truth, created Church courts (out of their sense of justice and fairness) to try those individuals who had embraced heretical beliefs, that is, beliefs contrary to the One True Faith.  These courts were known as Courts of the Inquisitions.

As many historians have recognized, the various Inquisitions were, in actuality, a very weak collective institution.  Even in Spain, one Inquisitor would be assigned an area that was a few dozen to nearly one hundred square miles in area. There was no way that such an individual could ever "patrol" such an area. As long as a potential heretic did not stick out, theologically, like a "sore thumb," you would not be noticed.

Even in Spain, it was not at all uncommon for criminals to "feign heresy," so that they could have their cases transferred to the ecclesiastical courts of the Spanish Inquisition.  Most heretics recanted their false beliefs without being tortured, and out of the many accusations, few heretics went to the stake.

While burning at the stake may seem cruel as compared to lethal injection, that form of execution was, in my opinion, a much better way to die.  As modern science has taught us, one was chained vertically, in the middle of a bonfire, and death would come from carbon monoxide poisoning long before one's body would begin to experience the physical fire.  This is why Inquisitor-General of France, Jean Brehal, at the Trial of Nullification of Saint Jehanne la Pucelle ("Saint Joan of Arc") stated, "Tomorrow, at the Old Market-Place, in the same place where the said Jeanne was suffocated by a cruel and horrible fire..."  The fire was cruel, but probably not the suffocating.  Jehanne probably died within the first minute or two.

In any case, being burned alive for a few minutes is nothing compared to an Eternity of torture and torment in the "fiery furnace" of eternal Hell.  Now it must be admitted that very, very few people really, truly believe in Hell, but from the vantage point of the One and Triune God, a Perfect Being, public opinion polls do not matter.  In the end what Christ Himself said will be the absolute truth, "Strive to enter by the narrow gate; for many, I say to you, shall seek to enter, and shall not be able." (Luke 13:24)  This verse of Sacred Scripture is almost universally ignored by Catholic (sic) theologians, even though it is repeated in the Gospel of Matthew. "To each his/her own," I suppose.

If you believe in the Enlightenment ideas of religious liberty, free-thought, religious and moral relativism, etc., then you believe in ideas that are foundationally contrary to all of the Catholic Faith and every true Pope has condemned such ideas as being absolutely heretical and contrary to the Revelation of the One and Triune God to humankind.

The various Inquisitions were a blessing not a curse. Heresy is to the soul what murder is to the body; why would anyone expect Medieval Catholic societies to tolerate the presence of manifest falsehood and error in their midst??? It is infinitely better to be burned alive than to die in one's heresies and sins and then go to Hell, the fiery furnace, which will last forever. Even an relapsed and/or unrepentant heretic at the stake could, in his or her final moments, make a Perfect Act of Contrition and, perhaps, pass into Purgatory instead of Hell. Condemning such obstinate individuals to the stake was the ultimate act of mercy.

Saying that the Inquisitions, excommunications, torture, etc. were wrong and/or immoral is to say that Truth does not exist, or is at least, "in the eye of the beholder." Of course, nothing could be further from the real Truth, which is the Catholic Faith, outside of which no one at all will be saved.