"defund the police" means "defund the police", it is a clear and unambiguous sentence. If you mean "let the police do their job", don't run on "defund the police". It's not that people didn't look close enough at the slogans (and by the way we have seen many cities actually defund their police depts so it doesn't help the idea that the slogan means anything else).

I don't think that Biden himself holds leftist views but he also did nothing to distance himself from this fringe, and if he is not neutralised by a republican senate, I think there is a legitimate concern that he will be held hostage by the left wing of the democratic party and apply many of those policies (not the least because Kamala Harris would if he steps down for health reasons).