It isn't uncommon to find yourself on the losing end of the union contract negotiation with little you can do about it. You give up your agency. The only things that matter are the interests of the existing majority which will often be prioritized at the expense of the minority (e.g. LIFO layoff practices).

I made one tenth the salary as professor while teaching as an adjunct in grad school despite having a similar course load. My uncle's union negotiated lay-offs of his division over another one. A lot of us have stories like this that left a bad taste in our mouths about unionization. Corporations can also be guilty of favoritism but they aren't supposed to be on your side of the negotiating table.