It matters if devs who depend on donations for a living get their donations cut because someone they know or even themselves do something China doesn't like.

With React it's different of course, objectively you're right, but subjectively, using React doesn't feel right if you dislike FB, and using FB technology can scare of customers if they get aware of it. If you want to trash a competitor in a space that's somehow privacy focused, just mention that your competitors tech stack is from FB!