Copyright certainly matters. It's a big deal legally and economicically all over the world.

Suppose that it's just a bad idea and shouldn't exist. Does that mean that I should release my code into the public domain? I think you could make a good case that even being totally opposed to copyright morally or pragmatically or otherwise, given that it currently is enforced in many places it's worthwhile to play along. For example, some people would prefer a world without copyright, but GPL their code, because it might prevent a greater evil.