This is bad. The Mere-Exposure Effect can increase the number of victims as AI CSAM can act as a gateway drug so to speak.
This is the justification for keeping the ban on legally culled elephants. Yes, a percentage of elephants are legally hunted to control population and fund national parks, but you cannot import that ivory because the thinking is it will create a market and that market will quickly turn to pouching.
The anology here would be, that poaching is a thing even though it's illegal, so say we found a way to create ivory that is indistinguishable from the real thing, without any harm to animals.
You can flood the market with it curbing the demand, and still continue to hunt down poachers.
There's an argument to be made that they might have an easier time claiming their ivory is actually fake but the real strategy is to make poaching just not worth the risk by inpacting the reward.
You described two different things: a psychological effect first, and then a market. The elephant example isn't mere-exposure.
Also, I'm not an expert on this but do we see more sensless killing by kids playing violent video games? This is usually the counter example to the exposure argument and I haven't seen it properly argued against.
In the US there's also been an interesting rise in sexlessness and male virginity recently [0] which is a fun one to compare with exposure to pornography. There is evidence that real-world conditions have a lot more to do with real-world action than pictures on the internet.
This is the justification for keeping the ban on legally culled elephants. Yes, a percentage of elephants are legally hunted to control population and fund national parks, but you cannot import that ivory because the thinking is it will create a market and that market will quickly turn to pouching.