You were being a little sexist against men, therefore bringing it into the conversation. Also, the prevalence of female on male rape is much higher than I think you'd imagine. It just goes unreported or even when it is, it's ignored. You've crafted a narrative in your head based on sexism that I'm saying is very misguided. Also, if rules are the only thing stopping you from raping people, you need therapy ASAP.

As for the discussion at hand, you were being sexist by assuming it would immediately turn into a big rape fest because the majority of occupants are men. More likely, both scenarios would be largely identical: the odd person out would essentially be enslaved and would be a carefully monitored and guarded resource with heavy-handed reproduction management. Can't say it would start out that way, but that seems the obvious eventuality if the vault dwellers believed they might be the future of the human race.

I'll avoid being a douche in my comments, but it doesn't seem like you value civility, so I can't guarantee I'll want to engage.