I'm divided on this. I used to be in favour of unions until the firefighters strike in the UK in 2002/03. The union led by a left-wing extremist called Andy Gilchrist was demanding a 40% pay rise!!!!! This was totally unreasonable in my opinion, and the strike action just put lives in peril. My view of unions took a real dive after that event, it was quite disgusting.
I think moderate unions are fine, unions led by anarchists are not.
How about unions led by conservatives?
They don't exist in the UK. The vast majority are a
de facto part of the Labour Party (some Union bosses think it's the other way round). Some white collar unions are *technically* non-aligned...
Most other unions are led by nutters (eg: the RMT)