One thing I think people - especially Bernie-fans - are forgetting, is that Biden isn't Clinton. They may both be "the establishment candidate" but there are some big differences in how they appear, how they behave, and on some issues.
I still think the choice for Biden not to run in 2016 to make way for Clinton was a horrible mistake, as Biden would have done better IMO. And he was younger then than he is now - if he's the nominee you're basically running two slightly-dementing geriatrics against each other.
To be clear, I'm not a big Biden fan - as I stated earlier, I put him behind Buttigieg,Klobuchar, Warren and Bernie in my personal preference. But there are good, valid, reasons to vote for him, and continuously calling people who do stupid isn't very helpful.