in the books, on their first meeting, draco says one sentence to harry and harry immediately mentally compares him to dudley dursley.

i think that sets the tone of their relationship more than anything else. draco is spoiled, and pampered, and arrogant, and kind of stupid. he is selfish, and his worldview is narrow, but its out of a kind of privileged ignorance.

when draco is truly confronted with the reality of the beliefs he holds, he finds that he doesnt have within him the kind of cruelty that following it through requires of him. but its too late, he's in too deep, and changing will have terrible consequences for him and his family.

but thats still just about how it would affect him. i think he's still the person who would be happy yelling "you'll be next, mudbloods!", as long as he didnt have to be involved personally