Sure I get that loads of people really hated Obama for lots of reasons. I sincerely don't think this is a racial thing though: it's a tribal thing, us vs them. Republicans are perceived as being on the side of Christianity (us) so they are given a lot more leeway in these matters, where Democrats (them) are the enemy of Christianity and every slight however small must be countered in the strongest possible terms (see: 'the war on Christmas' and other stupid shit.)

Would the outrage have been greater if it was Obama instead of Biden? Absolutely, I'm not questioning that at all. I'm just saying don't think there wouldn't be outrage against Biden just because he's not black.