You do lead a sheltered life, don't you. Do you really believe those girls who look 16 are all 18....and that they're totally enjoying getting it up the ass, mouth and elsewhere at the same time? Yeah, that's just what all girls dream of. Especially if they're getting shot up between scenes. Good healthy fun.
If what you think porn is really was true, it would be relatively easy to prohibit. Since the vast majority of women in porn and prostitution really want to be there, it is impossible to prohibit. That's the part you are missing.
The abuse of women in the sex trades is prosecuted as abuse. Being sex related doesn't change it into something else. Unless it is specifically consensual between that woman and that man. Yes indeed, women specifically consent to being beaten every day. So do men for that matter.