His support for segregation was 40 years ago, he came out and apologized. Normally this would just be pandering but he went on to become the right hand man to the first black president. He never rocked the boat and did exactly what was asked of him.
In America, the symbolism of this was huge. It's why Biden has such huge favorability numbers among African Americans.
His devotion to Obama gave him South Carolina and then super Tuesday. No one would consider him a racist.
I'm really not sure an apology, or the fact it was 40 years ago should really just mean he gets the slate wiped clean. Look I'm not saying don't vote for the guy, but a simple apology for helping to enshrine the system of oppression that was segregation is really not acceptable.
It also gives a little indication into why he might be closer political to a racist politician like Trump, over a committed anti-racist politian like Sanders. Out of those two, which do you think would have wanted to end segregation and which would have supported it? Then factor in what position Biden took. Then work out privately, where he might sit.
As for the 2nd point, where is this apology for supporting segregation? Is there a link for it? I have seen him comment on it, and for the most part I'd describe his attitude as fairly condescending and unapologetic.