I can understand the liberals being happy with Biden's feistiness, but I do think some people live in a message board bubble where they have come to not only accept over the top rudeness and spiteful aggression, but to prefer that way of communicating. It's fine on the internet, but in the real world, people don't like rude behavior and when they watch a debate, they like to, well, you know, hear what the debate participants are saying.
I think Biden won the debate, but I'm willing to bet that the reason the polling is so close is because a lot of people were not so comfortable with Biden's behavior. You can be strong and assertive without being rude. IMHO.