Well they're just as stupid as the internet edge lords and Bernie Bros that are on here bashing unions.
Firstly, they conflate all unions with the image of some white-working-class-he-man-in-Ohio from 1950. The Service unions are very different in attitudes than most of the Trades. Police and Firemen being even more distant.
Working my way through college I was in both Teamsters and then in the Ironworkers. One definitely seemed to cultivate more entitled assholes that hate paying taxes, than the other. I always got the sense Police and Firemen skewed even more into entitled machismo.
Of course it explains the hurt feelings, Bernie Bros being entitled misogynists themselves. Probably take the Firemen Endorsement of Biden as a personal betrayal.
The NEA, SIEU, AFSCME, UAW, are the biggest unions, and have always favored Dems. Also no wonder... these unions are more diverse and represent way more women than the others. They also trying to grow more. These are the guys going into Fast Food. Trying to help organize "those people".
I don't have the link on hand, but this political scientist had this great quote about 2016.
"The average Trump voter is depicted as a union pipefitter in Ohio, whose sister has a pill problem. But the mean Trump voter is the guy's Dentist who own three houses."
**important disclaimer!
my contempt is specifically for berniebros, not all sanders supports. berniebros being just the most toxic of the bunch that are over represented on gamer forums, or Jacobin.com. Berniebros might also include conservatives sockpuppeting as european socialists, just to troll dems from the left. The way they apply their rage so specifically on US dems is weirdly peculiar.