It could be a generic "underdog" background, which could have any number of reasons for it besides being the victim of racism. You could be the underdog because you were bullied for being a nerd and now you want to stand up and fight those who bully nerds.
Personally, I'd think game perks may the way to go, because otherwise you'd be saying that your flaw affects how other people think about you (which is not only a bit victim-blaming, but also borders on a magical charm effect), whereas flaws in D&D have tended to be about how you yourself think or act.