The ref is obliged to stop a game if it is in his view a head injury or a nasty collision between players. Any thing else and the game can only be stopped if the ball goes out of play. The sporting rule (where an opponent kicks the ball out of play) is not to my mind an actual rule. So it is up to the players. In this case the guy went down clutching his leg...hardly a massive medical emergency. Some players dive which is not very sporting, nor is pulling the jersey of your opponent. Many do this...who perhaps scream fair play when it suits them..
Doing something because someone else does is not always a good policy....
Football is no longer a sport...its a business.....
All that said...the Leeds manager showed a lot od fair play...when he really did not have too.
Well done him...