The real issue is that the monkey (or Stable Diffusion) cannot be sued in civil court for copyright infringement, so they can't be granted copyrights in the first place: it makes no sense to have one-way streets of legal responsibility.

Note that a human-made curation of AI or animal art is protected by copyright (e.g. you can copyright an AI art coffee table book). The original case involved an AI-generated graphic novel: the author could claim copyright for the whole book but not the individual panels.