His leg isn't involuntarily thrown towards his opponent because he has been pulled backwards.
His shirt is pulled before he sticks his leg out, it's dangerous play as he isn't in control - he is somewhat unlucky in that he was able to keep his leg low but it was dangerous to put his leg out like that while not in control of himself and could very easily have hurt someone.
Would all have been avoided if the referee reacted to the shirt pull in the first place but I can't see how we thought we had footage that showed it wasn't serious foul play.