The most common argument I’ve heard, totally boiled down: “unions just protect the bad workers and if there weren’t unions the best workers would be able to get get paid more than those guys”.

But I also hear this kinda stuff predominantly from people who aren’t in professions that commonly benefit from collective bargaining. Most pipefitters understand that even a free rider benefits from collective bargaining, and that without unions it’s more often a race to the bottom rather than getting obscene raises for meritous reasons. The dude who drives parts for NAPA or whatever is usually the guy to say unions are dumb