My big gripe with unions is the unwavering protection of their worst performing members.

Eg, that they necessitated so called "rubber rooms" like these in the NYC public schools, where teachers got paid to do nothing while waiting on arbitration.

https://en.wikipedia.org/wiki/Reassignment_center

I doubt you'll find many people in favor of how bad cops get protected by police unions either. At least in the US I'd much rather a broad social net so my health care and retirement weren't so directly tied to my job than a union specific to my trade.