Unfortunately , i've encountered this , and the outcome was FAR from amusing.
About 7 years ago, I went out to a bar with my now ex-wife, her sister , and 3 other female friends.
we got a booth together, and , quite obviously, got pretty ripped.
after about an hour or so, I excused myself and went to the restroom.
it was pretty empty,,, just another guy at a urinal down the way.
he finished taking his wizz, and kind of just wandered toward me, and looked at my penis ( as i was at a table with my horny wife, i should add that i was fairly -though not totally-hard, which didn't help matters any!)
as the guy walked out, he semi-whispered 'nice dick'.
I blew it off, and went back to my table.
A little later, I went to play pool , and i noticed the guy checking me out , again.
I called my ex over, and let her know what was going on, and SHE blew it off.
After about another hour, i had to go again, so i went.
this time the guy came in after me, and , while i was pissing, HE GRABBED MY PENIS while standing behind me.
Reacting out of instinct, i essentially hit the guy full-force between the eyes- KO'd him.
I ended up spending the night in detox rather than with my wife
i think he should have stopped while he was ahead.