When Incels say “it’s okay for men to sleep around but not women because fat ugly women can sleep around, fat ugly men can’t” it’s a non sequitur
For arguments sake, let’s consider both the position that casual sex is wrong and the position that casual sex is okay. If it’s wrong, then it’s wrong for an attractive person to do it too, if it’s okay, then it’s okay for an ugly person to do it too. Your appearance doesn’t determine morality (it’s also a non sequitur to say it’s okay for one gender to sleep around but not the other but I’ll get to that later). And even ignoring the flaw in using the logic that looks determine whether casual sex is okay, by their logic it would be okay for a pretty thin girl to sleep around, but they would still be against that because it’s about policing women for choices they’re okay with men making.
Also their reductive logic that fat ugly women can sleep around but fat ugly men are unable to ignores A. There absolutely are men who would turn a woman down for her looks even if it’s just for casual sex B. There are fat ugly men who have slept around too, a fat ugly man could have slept with a bunch of fat ugly women.
Also there’s the obvious non sequitur of gay people aside, if women aren’t sleeping around men wouldn’t be either. What men who say this actually mean but won’t say out loud is either they want women to sleep around but also want to shame women for sleeping around or they basically want a harem of women who are only sleeping with them.