My view is this.Peter wrote:An interesting theory. However, the monks had to go into town almost daily to get food so they would still have regular contact with the opposite sex even if there weren't nuns.
Yes, that is right with "regular contact" (no touching and monks cannot even be seen to be alone with female etc) and in public view so there is a perceive understanding that there is a distinct separation of monks from laypersons. Two completely different "world". There is "them and us" i.e. the holy ones and the lay persons where the line is drawn.
But if there are both sexes in the holy order then that can be seen as "them" in the holy "society" but like any normal household with both sexes except that they are monks and nuns in the holy order with rules but rules can be bent by the weak as we all know. Assuming the assumption of bending the rules in the mind of the people then that inevitability will eventually lead people to speculation especially by those with ill intend. So behind close doors people will think of all sort of possibilities where they consider the possibility of both sexes gravitating towards each others and so the probability of encouraging scandals magnify.
Therefore, there is different in terms of daily "contact" with laypersons in this sense.