"Republicans would hate him just as much if he was all-white, but the half-black thing is one more handy aspect to the general approach of their supporters hatin' him,"

That seems to mean "Republicans" aren't particularly against Obama because he's black, but "their supporters" are. But surely when people talk about "Republicans" in this kind of context they primarily mean people who are "their supporters" rather than just the registered members of the Republican party?

Surely it can only be "a handy aspect" to Republicans on any definition if they don't really like the idea of a black president. Whereas, on this analysis,if the boot was on the other foot, and the Republican candidate was black - perhaps Colin Powell - that wouldn't be "a handy aspect" but a real problem for "all the white Democrats who want to see themselves as righteous defenders of racial equality"?... (Which in the light of the history of the Democratic Party over its first century or so is a pretty bizzare turnaround!)