That's basically saying that you'd grab someone's crotch to steady yourself if it was what you could get a hold of.
The bit sounds like a cheap, crass joke aimed at making twelve year old boys laugh. I just don't see how it can be made to look realistic at all.
Naw usually if your reaching for the crotch it's much too late.
And I work in bars at night and have actually seen it happen... Your point? Of course usually it would be some ones friend and not a complete stranger. I also see it as a silly little thing to get all hung up about. IT'S A MOVIE, if it was an attempt at humor, yeah it will fail, but seeing as in the time I've been a host of Karaoke shows I've actually seen the situation and even though it would be a rare target it's plausable. Me personally would reach for whatever/whoever I could grab on to to keep me from falling, and apologize accordingly later.