The counterargument about grabbing your opponents shorts is a valid one. It could be that you can grab your opponents shorts but it is illegal to pull them down. it seems like it sure as hell would aid you in picking up your opponent for a slam if you can simply grab his shorts.
Also, a fighter shouldn't let his opponent get ahold of his arm to put him in a kimura. How many other times have you seen a fighter grab his own shorts to prevent a kimura? This is a first that I can remember; especially seeing as how this is the first time I've heard anyone question the legality of it. It seems like plenty of MMA fighters, all of them in fact, prevent a fighter from putting him in a Kimura by preventing the bad position in the first place, muscleing his way out of it, or contorting his arm out of it like Rich Franklin did against Okami.
There can't be a double standard. If a fighters shorts are something he can use to his advantage, then they are also something that his opponent can use to his dissadvantage.
Bye the way, use your noggin. The pulling the shorts down move you keep bringing up is completely retarded. I just don't imagine any fighter doing that. It would make him look like a ***got, and would also cause him to lose a point.