That is true in many countries - though there are some (US being one) where non-union employees are ostracized or pushed away from being employed, especially as the law allows exclusive union representation in about half of the states [0]. The unions have been known to argue for union members and sacrificing non-members as part of exclusive bargaining with the company.
> I know the issue has 1000 shades of color, but if somehow, someway, in a sunny day, with all the possible luck in the world, someone sides with you in a dispute (and is not a lawyer you are paying), that will be unions.
That's not being impartial - that is being on your side. Yes, there are conditions in which unions may be on your side (in which case: great, but still bring a lawyer) - but the claim in grandparent post is that they may be impartial, whereas they very rarely are.
[0] https://www.nrtw.org/your-right-to-work-rights-in-three-minu...
I know the issue has 1000 shades of color, but if somehow, someway, in a sunny day, with all the possible luck in the world, someone sides with you in a dispute (and is not a lawyer you are paying), that will be unions.