imo it just dosen't seem right...
you look at just about every other sport bar boxing

american football, swimmimg, athletics, world's strongest man, basball, bodybuilding, football, and just about every other sport you can think of..
They abhor violence and the last thing that particular sport wants is 2 guys bashing their skulls in, because it just dosen't make into a sport anymore..

In Ice Hockey you are supposed to play the sport you were trained for, and that's to score, defend, tackle, pass, etc....not to knock someone out and break their jaw.
Boxing's main objective is to fight the guy, not ice hockey's.....

I couldn't imagine that rule happening in football (soccer), it would cause choas and ultimately destroy the 'beautiful game' imo.