It's like countries like the Australia, Canada or the UK banning Japanese manga artwork to "protect the children." It's got precisely dick to do with protecting kids, it's just about thought policing.*
The reason CSAM/CSEM is illegal is because a child had to be abused/exploited in order to create it, not because it's disgusting or immoral.
*"There’s no way to rule innocent men. The only power any government has is the power to crack down on criminals. Well, when there aren’t enough criminals, one makes them. One declares so many things to be a crime that it becomes impossible for men to live without breaking laws." -Ayn Rand