I don't think that it was particularly dirty, or as dirty as some of the stuff he pulls. It falls in a grey area...it's not a clean move, but really, for a black belt, Tex should have had better positioning on the underhooks to prevent it. It sucks that he's out for a bit, but it is submission grappling, and he is a veteran, competing at the expert level.
I guess it's probably not quite as bad as the oblique kick, in my opinion. They both have potential to do long-term injury to the opponent, but leaving the opening for the arm crank is more a matter of poor form than with the strike to the knee. And yes, I get that they're both legal. I hope that changes.
I think without any doubt, jones will do whatever he has to to win. There just isn't a bit of concern about long-term injury to his opponent, as long as he wins. I think there are a lot of fighters who wouldn't do the arm crank--and good on them, in my opinion--but I'm betting there are just as many who will be looking for it now.
But ultimately, I don't feel like this is as bad as the eye-pokes, the spinning elbows to the back of the head, the forearms across the throat, etc.