"You ain't black" possibly the biggest gaffe in Dem history.

So long Dem party nice knowing you.
Over 90% of them will vote for Biden
No it's not, and unlike Trump, Joe has already apologized for his bad joke. Notice he was smiling and joking when he said it. Certainly Charmlegne the God didn't take offence to it, and carried on the interview that was in no way obsequious, or condescending to the candidate. They talked about meeting to continue productive discussions later on.
Unlike the vicious and partisan attacks that Trump has made against various segments of the population, NONE of which he has ever apologized for. What you clowns are seizing upon is that Joe misspoke. Everyone says things in the moment. It's what follows that matters. If you recognize that you said something stupid and apoligize for it, people move on. If you double down on it, then deny you said it, even when tapes show you did say it, and then say it doesn't matter, the stench of your hate and your insensitivity clings to you and never goes away.
Trump carries the stench of his hateful remarks against women, blacks, gays, jews, Hispanics like the miserable scowl he wears on his face most of the time. Because he doubles down on every hateful remark, and backs it up by stripping rights away from all of them, to pander to his White Christian base, and the racist hate groups who form much of the voting base he has left, especially now that the elderly have been tossed under the bus in favour of the economy.