What made the colonists think they were so Cristian if they were able to macre so many Native Americans?

DId they think they were being good Cristians by killing those who were different than them or what, how does this work? We dont; understand them, they are different, let's kill them and we are holy and god is on our side, how is this rational? This is all hubris and ego, nothign to do with religion. Where does hubris come from?