It really seems like a lot of the resistance to sex positivity comes from a desire to be able to appeal to a set of socially agreed-upon standards rather than do the work of asserting boundaries. Or, less charitably, out of a desire to artificially increase your dating pool by making people feel like they’re morally obligated to adhere to your standards for a desirable partner.
Higher partner count correlates with lower marriage success rate. Men have also had to deal with paternal uncertainty for millenia. Both are going to have a warping effect. And women are still so protected that men cannot unilaterally order a paternity test in France, so that isn’t going away.