Was burning heretics alive immoral?

Note:  The following essay should be considered deprecated.  The Medievals took their Catholic Faith seriously, and followed it to its logical consequences and conclusions.  (Secular historians are, by the way, sympathetic to the Medieval Church and to its practice of burning heretics alive at the stake!)  Muslim terrorists, take note, if Mohamed was an epileptic crank with delusions of grandeur, you're certainly throwing your life away, aren't you?  Professor Daniel Dennett is right, religion is just a parasite which infects the human brain, a meme.  Stop being stupid, which means stop believing, and start living!

Consider the following from the Fourth Lateran Council, which is recognized as an ecumenical Council of the Catholic Church and is even referenced in the current universal Catechism:
Canon 3. On Heretics

We excommunicate and anathematize every heresy raising itself up against this holy, orthodox and catholic faith which we have expounded above. We condemn all heretics, whatever names they may go under. They have different faces indeed but their tails are tied together inasmuch as they are alike in their pride. Let those condemned be handed over to the secular authorities present, or to their bailiffs, for due punishment...
Pope Innocent IV, of course, presided over and confirmed the Fourth Lateran Council, and in his Papal bull Ad extirpanda, he states:
"Innocent, the Bishop, Servant of the Servants of God, to his beloved sons, the heads of state or rulers, ministers and citizens established in the states and districts of Lombardy, Riviera di Romagnola, and Marchia Tervisina, salvation and an apostolic benediction."
So, clearly, Ad extirpanda is a Magisterial document.  Innocent's justification for the punishment of heretics is given later on in the document:
Law 25.

26. The head of state or ruler must force all the heretics whom he has in custody, provided he does so without killing them or breaking their arms or legs, as actual robbers and murderers of souls and thieves of the sacraments of God and Christian faith, to confess their errors and accuse other heretics whom they know, and specify their motives, and those whom they have seduced, and those who have lodged them and defended them,as thieves and robbers of material goods are made to accuse their accomplices and confess the crimes they have committed.
He ends his decree with, "Given at Perusio, 15 May, in the ninth year of our pontificate."

As Innocent IV states, heretics are "murderers of souls," and as such, they deserved the ultimate punishment.

Consider the Council of Constance, another ecumenical Council of the Catholic Church, and its decree against Jan Hus:
The most holy general council of Constance, divinely assembled and representing the catholic church, for an everlasting record. Since a bad tree is wont to bear bad fruit, as truth itself testifies, so it is that John Wyclif, of cursed memory, by his deadly teaching, like a poisonous root, has brought forth many noxious sons, not in Christ Jesus through the gospel, as once the holy fathers brought forth faithful sons, but rather contrary to the saving faith of Christ, and he has left these sons as successors to his perverse teaching. This holy synod of Constance is compelled to act against these men as against spurious and illegitimate sons, and to cut away their errors from the Lord's field as if they were harmful briars, by means of vigilant care and the knife of ecclesiastical authority, lest they spread as a cancer to destroy others...
Heresy is a cancer, and in our day, apparently, a terminal one.  The Council continues,
This most holy synod of Constance, invoking Christ's name and having God alone before its eyes, therefore pronounces, decrees and defines by this definitive sentence, which is here written down, that the said John Hus was and is a true and manifest heretic and has taught and publicly preached, to the great offence of the divine Majesty, to the scandal of the universal church and to the detriment of the catholic faith, errors and heresies that have long ago been condemned by God's church and many things that are scandalous, offensive to the ears of the devout, rash and seditious, and that he has even despised the keys of the church and ecclesiastical censures. He has persisted in these things for many years with a hardened heart. He has greatly scandalised Christ's faithful by his obstinacy since, bypassing the church's intermediaries, he has made appeal directly to our lord Jesus Christ, as to the supreme judge, in which he has introduced many false, harmful and scandalous things to the contempt of the apostolic see, ecclesiastical censures and the keys. This holy synod therefore pronounces the said John Hus, on account of the aforesaid and many other matters, to have been a heretic and it judges him to be considered and condemned as a heretic, and it hereby condemns him.
The late Pope John Paul II, a now-supposed Saint in Paradise, "apologized" for the actions of an ecumenical Council of the Catholic Church.  Would a true Pope or Saint have ever done such a thing??  Finally, the Council of Constance issues Jan Hus his just punishment:
This holy synod of Constance, seeing that God's church has nothing more that it can do, relinquishes John Hus to the judgment of the secular authority and decrees that he is to be relinquished to the secular court.
As I have pointed-out elsewhere, Pope Leo condemned Martin Luther's assertion that "It is contrary to the will of the Spirit that heretics be burned." (Exsurge Domine, #33)  And, theologians have always recognized this to be an ex cathedra pronouncement:

http://denzinger.patristica.net/#n700

Regardless of Luther's proposition "being heretical, or scandalous, or false, or offensive to pious ears, or seductive of simple minds," it is "in opposition to Catholic truth."

To say that traditional Catholics face a "serious ethical problem" in defending the good names of Catholic princes and churchmen, Popes included, who rightly and justly punished heretics within their kingdoms is like saying that we should not lock our doors at night or keep our children safe from sexual predators.  It is to say that a Catholic king should not protect his subjects from rapists and/or murderers.  For if it is moral and licit to defend against those who would destroy the body, how much more moral and licit is it to defend against those who would kill the soul?

How to reconcile the burning of heretics with Dignitatis Humanae?  I suppose that such would depend on how one chooses to interpret DH's "within due limits" and a "just public order" as well as Vatican II's other lip-service theology.  After all, a Catholic king may tolerate heretics within his kingdom as long as the "public order" was maintained, however, such would not be a "just public order."  For allowing a heretic to endanger the eternal salvation of others would be the supreme injustice.

It's "practical atheism" at work here, folks; we don't have to profess atheism, but we can act and live like we are atheists.