When genuine revolutionary cadres do form, they tend not to last long before the doors get kicked down by Witch Hunters or similar, who are often quite confused when they can't find the Vampire or proscribed cult they were expecting to be behind it. The Empire's many mechanisms for finding people who are Up To Something are frankly unfair when those in question are just regular people who are genuinely dissatisfied with the status quo. Survivors often end up in the Border Princes, which works as a handy safety valve for ridding the nations of the Old World of the chronically discontent.
I suspect that a Templar of Sigmar who just slaughtered a peasant rebellion against an unjust lord without meaning to would feel a bit more than confusion, maybe remorse or horror. They are pretty inured to killing cultists, necromancers and such but I imagine it would be a gut punch to find out 'no this time is was just hungry peasants'.