The Faith Militant were religious populists, yes — and also brutal thugs whose punishments were unjust

"The law” that concerned the High Sparrow was not the law of the State but religious doctrine in a kingdom that almost seemed pluralistic by default, with its key players too concerned with vying for power in this life to care about the next. Equal application of an inherently discriminatory law that derives its moral authority entirely from religious text, without regard for the spiritual beliefs of those to whom it is applied, is not a liberal value. (One is reminded of a rueful Anatole France on the “majestic equality of the laws, which forbid rich and poor alike to sleep under bridges, to beg in the streets, and to steal their bread.”) The High Sparrow’s dispiriting tendency to demand religious conformity with might was perhaps his most loathsome quality. His martyrdom might have been acceptable, heroic, even, if he hadn’t consigned Margaery and the citizens she exhibited clear concern for to the same fate, either by stupidity or by actual indifference to their lives. Forced martyrdom isn’t martyrdom at all. It’s murder."
read more
Cheering the High Sparrow’s death: Why the end of this “Game of Thrones” villain was so satisfying - Salon.com