Rincewind
Philosopher
The Cathar thought so, and look where it got them.
Indeed:
Arnaud-Amaury, the Cistercian abbot-commander, is supposed to have been asked how to tell Cathars from Catholics. His reply, recalled by Caesar of Heisterbach, a fellow Cistercian, thirty years later was "Caedite eos. Novit enim Dominus qui sunt eius"—"Kill them all, the Lord will recognise His own".