And that would be because in your opinion all union members give up their right to make up their own minds when they join the union (or in my experience . . . are forced to join the union).

I have no problem with unions. I have a problem with people who think unions (or management for that matter) are always right. If you know something about the dispute and you choose to support the union that is fine. But if you support them simply because they are a union then you you always support the union then you are acting out of ignorance.