I'm an old time leftie and have hated the way that both Harris and Booker have said, pretty much directly although tangentially, that Joe is a racist. First, busing was a GD disaster no matter your position on any policy matter. You also cannot be utterly present-determined when examining matters of the past. Anyone engaging in presentism in that way will be just as trapped in the future as those they condemn now.
No offense to her, but Harris is also pretty scummy in her personal life IMO. Booker is a shining example of good choices but he seems to be one of those "stars" identified when young, who basically decided to run for president when he was still a kid. I don't like those career arc stories very much, truth be told. It's part of the reason I never really liked Clinton, a future star in politics from the time he was a kid. Being excellent is great unless it's done to cynically drive future positioning.
Last, this busing garbage threatens to paint the dems into the position of supporting busing in the present, an absolutely disastrous corner to be painted into IMO. That's a national election-losing position folks, much worse than abolishment of private health insurance, which is bad enough.