The point Ron is making is that there seems to be a widespread expectation that musicians and other artists will work for free for any good cause that asks them to do so.
As Woody once said: "Lady, I've never worked for a bad cause."
When people ask me to set up an event for free, my response is similar to Ron's. If I volunteer, fine. If someone tells me to volunteer, that is another issue. I make it a point to insist that any performer I ask should get some sort of an honorarium. If they return it or offer to work for free, that is on them. The point is that performing is work.