What made them mad:
"Man I'm not happy with Biden winning the nomination. I wish I was Bernie."
"Well we can get Trump out of office and then you can push him to the left."
"Fair enough, a moldy ham sandwich is better than Trump. Biden can string words together so that's possible."
[One presidential election and mid-term later.]
"So Biden hasn't pushed Congress on most of his campaign promises, and he's enabled racist policies Trump wanted to try and win moderates. No abortion, no DREAMers, no minimum wage increases, no queer protection, but they can find time to ban hoodies in Congress. Not to mention ignoring voters who care about Ukraine and Palestine. It feels like Biden isn't great for Americans, he's just slightly better than Trump."
"Why are you so anti-Biden? Are you some kind of fake leftist or a Russian agent pretending to be American?"
"No? I'm trying to push him left. I'm saying he's not doing things for most of the people who voted for him to be better. His biggest actions are done by appointments, by him to the FTC and FCC. Not a lot of bills passed."
"I think you just hate what Democracy is, he's not a king."
"Right. But Republicans can pass without issue, and Democrats want to work with them instead of getting progressive voters."
"You're biased and nitpicking, so I win."
Honestly if there are Russian agents at play it's probably these people trying to further drive a wedge between leftists and moderates. I've seen plenty of threads where even the most moderate criticism of Biden is dismissed as vocal support for Trump and trying to spread voter apathy.
The thing that actually spreads apathy is this behavior. Yes, you should vote for Biden because harm reduction is always better than nothing. But you shouldn't have to be happy about it.