My work does not, I repeat, does not belong to all humanity. Humanity has never in its long and illustrious history written a damn thing. Saying that a particular work of art belongs to "humanity" as opposed to the artist who made it makes about as much sense as saying that your car belongs to humanity.
Stop equating creative output to tangible things. They are simply not the same. If somebody took your car, you couldn't drive drive it or use it or sell it any more. No one can take your creative output away from you, they can only make copies. Your argument is that could reduce your income, and that is quite possible, that does not make it theft though. I suppose it comes down to the concept of owning ideas - a concept I reject. You don't want anyone else to copy your ideas or content, do not release it, that is the only way you can ever actually achieve that.
Term, holidays, term, holidays, till we leave school, and then work, work, work till we die. -- C.S. Lewis