And so there's this half of the issue, the idea that Muggleborns are useless and worthless, and should just go away, which Lucius seems to adopt so fluidly, and which Draco probably thinks he is adopting by calling Hermione a Mudblood and reminding her of her worthlessness (only he's not, since he singles her out with this insults and copies all her ideas). And the other half of the issue, the recognition that Muggleborns are intelligent and good wizards/witches, though a wizard may by far prefer his kind. This is more of the side that I've seen from Slughorn. I don't see him as actually thinking that they are inferior, but rather thinking that they should be inferior I'd have a hard time picturing him finding amusement in a "Mudblood" insult, but similarly, I'd have a hard time picturing him actually making an effort to enforce equality. And if this Hermione-Draco arc ends up going anywhere, I really don't see it having further results than this latter side, because Draco is already so deep-rooted in his prejudice that even if he admits that Muggleborns are not worthless and can actually be even more impressive than some purebloods, it's unlikely that he'll be able to meet a Muggleborn and not be a little surprised, even in an "I should have known" way, when they prove themselves to be intelligent and even "superior". Like, I'm finding it hard to believe that any amount of consideration over Hermione's abilities will lead him to look at, say, Colin/Dennis Creevey or Justin Finch-Fletcheley, and not see inferiority, even if he doesn't want to kick them out of school anymore; because an exception may cost him to look at Muggleborns in a different way, but not exactly to look at ALL Muggleborns in the same way as he looked at that exception.