Oh get a grip.
There's nothing wrong if you've had no sexual partners, ten sexual partners or ten thousand. It's disgraceful that people (men) judge others (women) poorly because they are seen to enjoy sex with numerous people.
If they are safe, and happy then what's wrong with it? And the suggestion that they wouldn't do it if they were happy is nonsense. Sex is fun. Sex is enjoyable. Sex is good for you! 
Again, there's nothing wrong with sleeping with lots of different folk. Nothing wrong what so ever.
Just read this. Could you get any more sexist if you tried? Men are not physically and/or emotionally superior to women in today's world. Why can't a women enjoy herself? Who are you, a man, to say that that person can't do what THEY WANT TO DO because they are female. You're attitude is abhorrent. And I'm very surprised, and disappointed by you.