Not really my thing here since i'm belgian and we have multiple cross industry unions competeting. However from what i hear about american unions it starts to sounds like an argument for acting and arguing against a union if it leans against your politics and you don't have enough influence whilst also not doing enough towards your wage/work conditions.

I don’t want to waste time to fight battles within the union. This is exactly what I’m talking about. If it’s just a political nonprofit with forced donations, I’d rather see them banned than join one.