The argument is that the use of “porn” implies that it’s as acceptable as regular porn, that it ligitimizes it.
Which is absolutely ridiculous. Only a pedophile would see “child porn” and think it’s just another perfectly acceptable category of porn.
But some SJW think tank probably got a grant and a few professors got published due to this.
My guess is that the churn in PC terms is similar to the way software companies always have to release an “update” or “new feature” even if their product is working perfectly fine: people need promotions, and big initiatives make them look good, and they nope out to another company before the negative effects can be seen, so future employees who are stuck with the stupid unnecessary change get the blame for its failure.