There was for a time but there is no longer another progressive candidate to vote for. I don't disagree that most people don't vote for policy per se but on personality and other traits they think they can perceive. But I think the number of swayable Democratic primary voters who hadn't already made up their minds *and* are on Twitter is a lot lower than it's made out to be. Again, I'm not saying I think being aggressive and mean on the internet to supporters of other candidates is a good idea. The expectation that Bernie more than any other candidate should write an op-ed to denounce them or go on MSNBC, where his even addressing it would lead to two hours straight of "his supporters are toxic; he just can't win". More voters watch that shit than are on Twitter. Then that stays in the news cycle another few days until he's asked about it again, and it doesn't go away despite his being very clear about it.
Also he's made his case very plain to moderate voters, I would say. He's been clear that his campaign's goals are to increase the quality of life for people of all social classes, races, educations, etc. To tackle inequality, health care that leaves out the most vulnerable and still takes more money from your pocket than universal would, climate change, and neverending war. More than any other candidate it's been exceedingly clear what they're fighting for. If a moderate can see that message and not support it, what is he supposed to do? How much bigger does a tent get? Does he invite the person who brought the swastika flag to his rally last night, too?
Campaigns are not their most vocal, obnoxious supporters.
Sure. That is very unfortunate. I think people everywhere are learning as they go in the new world of elections in the Internet age. I certainly agree that I don't think acerbic wit or sarcasm, like perhaps the "If you don't like Corbyn you can fuck off and join the Tories" quip you mentioned, is constructive in terms of outreach. As mentioned earlier, I think the "Bernie bro" narrative is very easy for some people and certain media to latch onto and make it a story, especially in the absence of actual dirt or substantive criticism of the candidate or policy itself. I understand that this happens. It's frustrating. It's especially frustrating when, for example, Biden himself responds to a man asking about immigration with "You should go vote for Trump" before he's even done asking it. That's actively shooting down someone looking to improve a certain area of life or politics because they don't fall immediately into the camp the candidate is already in and he's not going to entertain listening or changing his mind. But that's not in the news cycle for four years. Decisions are made as to what's in the news and after a while it becomes "fact" to a lot of people, especially those who maybe don't have the time or energy to dig much deeper.