In order to establish a pattern of "papish" abuses before the widespread massacres of nuns and priests, your source relies on identifying Albigensians as Reformed Christians, since the Catholic Church did use violence to suppress the Albigensian movement.
This is quite a desperate tactic, very surprising to me, since the Albigensians' beliefs are so anti-Christian that they are not even referred to as a heresy by the Catholic Church, but an apostasy. The closest comparison the Albigensians have to a modern cult is that of Wahabbism, but even that does not approach the fanatical zealotry of the Albi, who commended people starving themselves to death as the only sure way of earning salvation.
Nonetheless, the Catholic Church was concerned that the suppression of such heresies and apostasies by secular authorities, falsely claiming clerical authority, was dangerous to Christianity. Attempts at selectively blessing certain kings (Holy Roman Emporers, such as Charlemagne) while excluding their rivals was only marginally successful, and bred disloyalty among those kings who would not be so blessed. Further, Kings regularly claimed "divine right," in defiance of the Church's lack of blessing.
Hence, the Inquisition was founded. Unfortunately, Protestant sources such as yours conflate the Inquisition with precisely the barbaric practices it was intended to prevent.
The Inquisition was charged with a difficult task; it represented the Church, so it had to be a sense of forgiveness, redemption, and charity; yet it also had to be effective at suppressing revolt, to maintain credibility with the kings and to fulfill its basic functions.
Whereas secular authorities imprisoned and killed with very little evidence, often on assertions they were "defending the faith," the Inquisition looked to the bible for rules of conducting a trial, introducing such notions as corroborative evidence, concurrence of witnesses, etc. It also found that torture was widely used by kings as a means of terrifying their population, rather than intelligence-gathering. Therefore, sustained torture, although very common among Protestant movements, even in the American colonies was forbidden; Inquisitors realized if an accused terrorist didn't talk in the first fifteen minutes, he wasn't going to talk; they successfully implemented practices recognizing this.
Tragedies such as Bartholomew's Massacre (wildly exaggerated in many sources) demonstrate not the sadism of the Inquisition, but that a desperate public found the Catholic Church's official actions wholly inadequate, and took matters into their own hands.
I think you meant to say, the other side of the issue as you only posted one side, not both.
You are seriously embracing the Albigensians/Cathars as Protestant Christians?