My two cents: there really isn’t anything mysterious here that requires subtle reasoning and speculation. The Left doesn’t dislike Pete because he’s young and gay; we dislike him because he is a centrist, and he has distinguished himself in the campaign by attacking Leftist policy priorities with GOP talking points (in other words, he started it). I can attest to this anecdotally, since I’m gay and Leftist, and I can’t stand him. Before I explain why, the following caveat: if he were the nominee, of course I would vote for him, and even work for him. One wonders whether many of the Blue no matter who can say the same about Sanders, btw. Now the reasons. First, so-called centrist democrats don’t seem willing to accept that Leftists have core principles, and mean what they say. Taking corporate money is a non-starter for us. We really mean it. We’re not kidding. It has something to with why we are not centrists, btw. Next, we don’t share his optimism about common ground with the people who have voted for Trump. We have given up centrist dreams (because its a moving center of continual appeasement) and we have accepted that we are engaged in political struggle (by both electoral and other nonviolent means). There is also the fact that we have seen this all before. Obama was what we on the left call a “progressive neoliberal.” By this we mean that he peddles hope based on identity politics, but fiercely protects economic status quo ante. If you think Obama is a good part of the reason why we are where we are today, then you are a Leftist. If you think Obama was great, and that liberal complacency with growing inequality and other ills had nothing to do with rise of Trump, and you just want to return to the head in the sand good old days then you are still (as hard as is it is for us leftists to imagine) and think we can win by doing so, you a centrist. More: your point about young and gay just doesn’t resonate. Young people flock to Bernie, because he stands for significant changes in the interest of a livable world for the next generation. Leftists don’t hate him for being young and gay. This is because the young and/or gay are increasingly leftists, and its mostly old people who like Pete. Which brings us to Biden. Biden is still living in 1979. We don’t expect him to understand that the prior centrist consensus has been murdered and buried by the GOP, likely never to return. Our view is that Pete should know better. We expect that he does know better. But Pete wants us to believe that he can talk to the money, do its bidding, yet somehow direct it, tame it, and get it to play nice. So we just don’t trust him.