I was reading this "How To" book at Barnes & Noble a year or two ago, because it looked like a breezey novelty read about all kinds of interesting stuff.
One was "how to fight" -- shit you not. There was a book, or at least a novelty book, attempting to teach people how to fight.
The first step, of course, was avoid at all costs blah blah blah. The second step, before the actual fighting, was to slap your opponent with a firm, open palm in the face when he first approaches you.
Not violently, just enough to get their attention.
The idea, of course, is to confuse him and weird him out so that it diffuses the situation.
I instantly knew that was bullshit, even though I've never been in a physical fight in my adult life. That shit will only piss off like 99% of the people you're fighting, myself included.
But the depantsing move... sounds like that move has the spirit of the slap idea, and might actually work.