Perhaps I'm naive, but I think most men would refuse to participate. Speaking for myself, I can't imagine sharing a sex partner; moreover, I'm pretty monogamous -- were I not already married, I think my dating would be oriented toward getting married, and again I wouldn't be inclined to share.
Then again, I'm an engineer by inclination as well as career -- I've never been on what you might call the cutting edge of sexuality. So I really can't say what "most" guys would do; all I really know is that, with all of the guys I know, I've never been in a position of even having to make the decision. Perhaps I'm a wet blanket, or maybe the guys I know are birds of a feather, but it's just not a situation I've been in.
I suppose it's too much to imagine most men would not only not participate, but try to stop it.
Again ... I think most guys who'd be inclined to "stop it" would be like me, and not be in the situation to begin with.
That makes sense. I can't imagine any of the guys I know would participate in that sort of thing, but sometimes I think maybe I've led a sheltered life. Thank goodness.
susie