A similar sitch happened to me once only it was OBVIOUS to ALL THE MEMBERS THAT I WAS MARRIED WITH A HERD OF KIDS...BUT this disgusting bitch-titted, pot-bellied old child-molester looking dude would STARE ME DOWN CONSTANTLY...we are talking drooling and undressing me with his eyes. True, I don't wear a WHOLE LOT when I am in the gym often times, but still...guys wear string tanks and shorts but chicks don't sit there and fucking salivate over them.
Anyway....he would do this ALL THE FUCKING time and though he would never say anything to me it really fucking creeped me out. It gradually progressed from him staring at me from across the gym to manuevering his disgusting self to within a few feet from me REGARDLESS of where I was or what I was doing. Finally, I fucking choked and lost my mind. You know what I did? I fucking went running to my husband and begged him to say something to the guy so that he would leave me the fuck alone.
Moral of the story? I felt like a pussy. I felt humiliated. I am grown and I should have been able to turn around and tell that motherfucker, "TAKE A PICTURE, IT'LL LAST LONGER!"...or something rude like that. He would've went running to the opposite end of the gym and probably NEVER looked my way again.
My ex constantly gave me shit about what I wore and who I talked to etc...the ONE TIME some asshole really stepped out of line I fucking choked and had to go running to him to help.
Unless the guy physically TOUCHES your wife or girlfriend - WHATEVER - YOU SHOULD STAY OUT OF IT! She should have the backbone to tell him, "Thanx, but no thanx" in no uncertain terms. I hate to tell you, but just because girl has a boyfriend DOES NOT MEAN she will not go out w/another guy. (NO DISRESPECT TO YOU OR YOUR GIRLFRIEND...Just stating a fact.) So she needs to tell this guy, "Dude, I am very flattered by your persistence, but my current boyfriend makes me very happy and you have ZERO chance w/me, but I'll take your number in the off chance that hell DOES FREEZE OVER...KAY?!"
By you threatening the guy, nothing will change. She needs to stand up for herself and you need to tell her to do it. She will feel better and so will you.
PS - I HAVE NOOOOOOOOOO PROBLEM TELLING ASSHOLES WERE TO GO NOW AND EXACTLY WHAT TO DO WHEN THEY GET THERE!
...just my .02