I think libs just come up with that stereotype about conservatives, to make their horrid over the top acting out behavior justified. You make a good point about women in monogamous relationships being the most satisfied and that is a very good point on the conservative end of things.
When it comes to sex, liberals look like they're trying too hard... When liberals have to flaunt their sexuality, talk about it endlessly, and use all the "things" they have to use, it might just mean they "don't get much satisfaction..."