There's little understanding of the "right to work" law. It's actually very beneficial and unions don't like it. Here's the basic gist... A company can fire you for no reason but they can't fire you for ANY reason. When you're in a union, you have basically no right to sue for wrongful termination. It has to all go thru the union and as you can probably guess, the unions are useless in this respect. What can they do really to help you? NOTHING!
But the threat of a lawsuit when you are terminated will get you multiple reviews and writeups and probably severance before they fire you. You'll get several chances to defend yourself and even more after they fire you.
Basically, if they fire you, it better be because your job is being eliminated or you did something catastrophically stupid and/or undefendable.