Not saying you should vote for Biden, I think you should not (and instead vote for something cool like, idk, PSL or whatever the fuck you guys can vote for, just to give them enough votes for the uptick to be on the radar). But when you're talking to people who are going to vote for Biden, just don't dwell too much on the thing. It's not worth it, it is quite likely you will just piss them off, and chances are you won't convince them. If you want to talk about how both Trump and Biden suck, alright. It's just... I can see how this could push their buttons very easily. Just my opinion.
Trying to shame people about their voting habits have been repeatedly shown to be the most useless way to talk politics with someone. If you do break through to them, chances are all you'll do is disenfranchise them and make them give up generally on participating in politics.