Once upon a time however, he truly did believe everything he had been taught about muggleborns. Why wouldn’t he? He didn’t know any muggles, he had only been exposed to other prominent wizarding families, his parents were both powerful members of their community, so there was no reason to think outside the box. It wasn't that Granger was the one who necessarily changed his beliefs, but at some point in time, a person passes that point of no return. And for Draco, that point was when a megalomaniac took up residence in his home, and forced him to watch his former professor get eaten by a snake. Was it really so terrible to let people born with magic keep their magic? Again, perspective.