You do love your labels and then slotting people into them to suit whatever "argument" you are trying to make, I find it pretty bizarre but each to their own.
The "left" as you label them do tend to give a crap about workers more than others. That doesn't give them a free pass on f-cking things up or being held responsible for it, anymore than anyone else.
Pretty sure, this whole back & forth is because Polly is demanding to work there but doesn't want to join a union even though that's a condition of joining. If the existing workers want to change that, then they can, onerous though it may be. If the union is not working for them, then I expect they would - it is America after all.
Generally, as I've said, I have no issues with unions, but have never been in one so have little practical experience of them. I can see, and experience daily, the good things they have delivered to everyone.