I'm getting tired of my former Sanders-supporting friend's heal biting

I'm a musician and most of my friends are/were Sanders/Warren supporters. One of them posted an article about Sanders telling his supporters that refusing to back Biden is irresponsible. She agrees, though not happily, and is urging her other progressive friends to fall in line.

My lefty friends, whether FB or long time friends, almost all are voting for Biden, but here's an example of a response to me saying I'm glad to vote for him, included info on AOC and other progressives being part of his team:

"I think he is losing it. He is really old and he doesn't have Bernie's level of focus. There were so many sharp, young candidates. Sigh. We can only hope that he surrounds himself with good people."

I do think the "Black Trump voters" comment is a big turn off for them.

Sorry, had a moment there, and it's not Joe's comment that has me banging my head.

I'm carefully coaxing them along, I don't hammer my points, concentrate on policy, his collaboration/compromise on policy with progressives, etc.

How do I answer this negative shit?