I can also see the argument that a cultural symbol shouldn’t be something that’s privately owned, but the problem I see there is that within a capitalist system that becomes a form of disprivlage. Basically, he’s an artist working to represent his people, and artists deserve to get paid even when they’re doing that. Most representative cultural symbols don’t emerge organically, so someone has to design them. Stiffing them seems wrong, and copyright is actually doing what it ought to when it makes sure the artists are paid. But that only works if they get decide who gets to use it commercially.
Gilbert Baker’s gift of the Rainbow Flag was an amazing act that enriched the LGBT community and the world, but it had to be his choice. Otherwise his artistic autonomy means nothing. Thomas chose the opposite, and much as we might not like it, I do believe it should be respected.
Anyway, just my opinion, and something I think reasonable people can disagree on. As I said before, the wider cultural significance of his design is the aspect to which I’m most sympathetic.