Forced conversion is contrary tot he teachings of the Chruch and always has been. Do you have a specific example that we can examine?
they were doing so as agents of the Roman pope
There was no agency relationship between the feudal sovereigns and the pope ever.
What was their offense, other than "heresy?"
The Albigensian crusade was a crusade, and not an inquisition. Like the Muslim in the Holy Land, they usurped territorial control in Southern France. Whatever your objections to the crusades are, what do they have to do with the inquisitorial methods?
I think you should take up Campion's advice.
In 1231, Pope Gregory IX published a decree which called for life imprisonment with salutary penance for the heretic who had confessed and repented and capital punishment for those who persisted. The secular authorities were to carry out the execution. Pope Gregory relieved the bishops and archbishops of this obligation, and made it the duty of the Dominican Order, though many inquisitors were members of other orders or of the secular clergy.
The Albigensian crusade was a crusade, and not an inquisition.
A later pope, Pope Gregory IX established the Inquisition, in 1233, to combat the heresy of the Abilgenses, a religious sect in France.
The express purpose of this original medieval Inquisition was to discover and eliminate vestiges of Cathar belief left after the Cathar Crusades. ... In 1233 the next pope, Gregory IX, charged the Dominican Inquisition with the final solution: the absolute extirpation of the Cathars.
There have actually been several different inquisitions. The first was established in 1184 in southern France as a response to the Catharist heresy. This was known as the Medieval Inquisition, and it was phased out as Catharism disappeared.