I agree that the term 'slut' is applied generally to women (indeed, I just went looking for a male equivalent and couldn't find one, although I do know several people who apply it regardless of gender), and I apologise. I also agree that there is a double-standard, but IME it's not quite in the same place as you say.

IME, the "anyone who (openly) enjoys sex is considered promiscuous" (and therefore bad) idea applies equally to men and women. However, for men being seen as 'bad' is often (perhaps generally) regarded as a positive thing (by other men), and this I think is the double-standard. By the lights of the churches which disapprove of sex the men are also being 'wicked', but women are punished harder for unacceptable behaviour (probably because their priests are also male).