It's a naive approach to think cards will deter bad tackles, if thats the opponents tactics the rules are already in place and they are flouting them anyway to try to win.
You can't completely deter or eradicate bad tackles. Sometimes they will happen due to a split second difference in timing, human error or misjudgement, weather conditions, or simply the way the recipient of the tackle lands. You can help minimise them though through education; through training and through appropriate punishment. Unfortunately, football is often a subjective game divided by differing opinion both on and off the pitch, and between officials, players, fans and media pundits. This is a good example of where video technology could aid the referee in making the correct decision and award the appropriate punishment. He had enough time talking randomly to players that could have been better spent reviewing any available footage. He didn't see the tackle, he followed the ball down the line. Instead the fourth official provided an account even though his view was obscured by the away dugout and management. He got it wrong and the player has escaped the proper punishment and as a result has not received the requisite re-education on his tackling.