I agree that you cant just take men of the ball, that would be silly. But you have the likes of Leinster running very good lines in twos and threes and well timed flat, short balls then you cant let them through. If BOD had been further away from the ball carrier then i would agree, but one offload and he is through, you have to defend the channels. Most players would have just dropped the shoulder on BOD which would probably be worse.
Fantastic tackle, not even borderline, he kept control of BOD and never went beyond horizontal, seriously lads if you dont want to see this type of tackling go and watch football and stop spoiling rugby union. In the modern game you have to take out dummy runners, the ball could have easily gone to BOD and if BERGAMASCO had let him through we would all be laughing at him. A penalty would have been harsh.