Music is an art form. The principal motivation for artists is to create art. If you can get paid for it, even make a living at it, that's a bonus.

"if it IS your chosen form of work, then you should darn well be paid for it, in a generous and respectful way.."

Of course, and I don't think anyone has disagreed with that. However even a professional musician should also be free to decide when NOT to get paid, and to perform for the love of it. The OP has come close to criticising them for agreeing to do such a thing.

This thread originated because a free festival didn't pay its performers. It didn't refuse to pay them previously agreed fees, they performers agreed to appear for nothing, for the love of it. Lizzie seems to think that's wrong. No one else agrees.

There are situations where musicians really are exploited and those should be criticised. However the OP should direct her fire against these. Playing for nothing does not automatically equate to being exploited.