I've noticed that conservatives who are eager to make the first claim are very reluctant to admit your take...

But on a more serious note, I think that should be easier.

1) As people who have been maltreated for centuries, I suspect Black people might have a keener eye for it.

2) Democrats may not do enough for minority communities, but they are the only party doing anything at all. At least anything positive. So it's less obvious than Republicans who are very open in their disrespect for everyone of any color who isn't rich.

3) As mentioned, Republicans have been pretty open about their opinions. For anyone who doesn't realize that, may I recommend Reagan advisor Lee Atwater's comments:

"You start out in 1954 by saying, 'N*****, n****, n****.' By 1968 you can't say 'n****'-that hurts you, backfires. So you say stuff like, uh, forced busing, states' rights, and all that stuff, and you're getting so abstract. Now, you're talking about cutting taxes, and all these things you're talking about are totally economic things and a byproduct of them is, blacks get hurt worse than whites.… 'We want to cut this,' is much more abstract than even the busing thing, uh, and a hell of a lot more abstract than 'N****, n****.'"

4) One reason African Americans stick with Democrats in a lack of options:

"Now, you're talking about cutting taxes, and all these things you're talking about are totally economic things and a byproduct of them is, blacks get hurt worse than whites.…"

In other words, white voters are willing to be played by Republicans as long as it hurts Black people more — hurting Black people is a positive for GOP base voters. They’re willing to trade some of their prosperity for the chance to do so.