We've had black candidates run from both major parties. Please show me where these were treated with hostility or marginalized by any sizable group because of their skin color.
Nah, I think I'll take a pass this time, at least for tonight. It's certainly a rousing enough challenge, and I would actually be most interested in reading up on a couple of specific case studies, so I might get back to it later. But unfortunately I do not exactly have the kind of archive at hand here that would allow me to reach out to some folder and pull out a bunch of relevant newspaper articles. They could surely be Googled up - I, for one, remember reading several relevant stories, about parties suffering from part of their base abstaining or crossing over because of an ethnic minority candidate, or parties choosing not to even take the risk - but it would involve quite a bit of time to seek out and doublecheck a number of examples.
[Edit: this is where I originally wrote something about how you tend "to call on people to go through such exercises to 'come up with proof', only to gloss over the resulting findings" if they do - but I realise that was a bit unfair to you (of all people), actually. Chalk it up to a general frustration.]
In any case, considering the point I made was apparently obvious enough for even someone generally in such disagreement with me on these matters as Timber to assent, perhaps it isn't necessary this time anyway. For one I would suggest that there is a reason why there have only ever been two popularly elected Black Senators* and one elected Black Governor** in all of US history - beyond some sheer mathematical freak coincidence or hypothetical particular unsuitability of African-Americans for the office, that is ...
(*Edward Brooke in 1966, for Massachusetts, and Carol Mosely Braun in 1992, for Illinois.
The only Black Senators before Brooke served almost and over a century before him: Hiram Rhoades Revel was appointed in 1870 and Blanche K. Bruce in 1841, back when Senators weren't popularly elected yet.
**Douglas Wilder in 1990, in Virginia.
Before that the only Black Governor had been one Pinckney Benton Stewart Pinchback, who in 1872 was appointed as acting governor of Louisiana and served for six weeks.)