There are many publications studying how porn exposure shapes sexuality and our vision of the human body, especially in the young age, but not only.

By your logic, CSAM consumers would be "magically" unaffected by viewing this porn subcategory.

How convienient.

Read carefully: I'm only claiming absence of (genuine) evidence, not evidence of absence.

Until genuine evidence is available, either outcome seems plausible. It could be that consuming CSAM pushes people towards committing sex crimes, or it could be that it "magically" doesn't, the same way people playing violent video games are "magically" unaffected by doing so.

ETA: An example of the inability of porn to influence sexual behavior is the plight of gay Western men in the 1950s-1980s. During this time homosexuality was absolutely demonised across essentially all of Western society, so there was ample interest from gay men in "correcting" their "errant" desires (this is not to say that all gay men felt this way). At the same time, heterosexual porn was widespread and easily available, though admittedly to a lesser extent than it is today. Given these forces at play, if it were possible for a gay man to develop an interest in having sex with women merely by looking at heterosexual porn, it does seem like there would have been large numbers of gay men who successfully "converted" to straight men. But AFAIK it is disputed that any such genuine conversion has ever taken place.