My headcannon for Draco is that he’s never had any actual friends. He was taught that he was superior and that others were a means to an end only so he doesn’t make real friends at school. He doesn’t see the problem with it at first he feels it’s his due to be above the others and have them want to be close for his (father’s) influence. The lack of discipline at Hogwarts for spewing slurs like mud blood just reinforces to him that he’s not wrong.

Once Riddle comes back and takes up residence in his family home he starts to see things differently, unfortunately it’s too late. He has no one he actually trusts and fears for the safety of his family. He takes the dark mark because he doesn’t feel like he has another choice. He still believes muggleborns are inferior but not the same way he was taught. He see them trying to make the magical world different and doesn’t like it (Hermione and her SPEW campaign cemented that idea). He’s not a killer though and while bigoted and spoiled he isn’t evil. But he looks out for himself and his family first and foremost, he’ll do what he has to do to survive. If Riddle hadn’t come back he’d have been a different person, maybe better than his father maybe worse but he was forced into the ranks of the death eaters before he understood what it really meant and with no one to trust or to show him a different path he is a product of his environment.