I think it's particularly powerful because of past gains regarding more overt racism. If you're going to do racism in any sort of mainstream environment today, you have to at least dress it up with some plausible deniability. You don't hate people because they're black or brown, you're concerned about "crime" or "culture." And an increasing number of people are able to see through those dogwhistles, too.

For your conscious, unrepentant racists, these are surmountable rhetorical obstacles. But for those who aren't consciously racist, maybe who just grew up in conservative households/areas, or who aren't too political to begin with? They're in an environment where racism is widely considered bad, they think of themselves as good, so they believe they should oppose racism. So when you show them how racism is baked into all sorts of American institutions, they have to square their comfort with those institutions with "I'm a good person and should oppose this." Not all of them are going to change their beliefs to resolve that contradiction, but some will.