"Seems like the first part of that law would be struck down on First Amendment challenges."

Should be, but I wouldn't bet on it. We can see what states have been doing about "child sex abuse material" and arresting people for fictional stories, animations, etc on the theory that it might contribute to viewers becoming predators. It's disgusting stuff to even think about in this principled context, but it's wild that something fake is treated basically the same as the real thing. That's a lot of maybes and what-ifs resulting in child abuse convictions for something fictional. Might as well start up the pre-crime division.

Edit: Why do people disagree? Is it just because it is repulsive? Or is there an actual legal theory and material harm you are thinking about? If it's just "gross", isn't that the basis for many people's anti-gay stances, and how is this different?