Tackling. Should it even exist?

After watching the Browns Steelers game (WooHoo Steeler Win!) There were several times throughout the game where there was a tackle where the analysts were questioning whether it was a legal hit or not. For example, Steelers All-pro Linebacker James Harrison hit Browns All-Pro returner Joshua Cribbs with his helmet.Yes, it is a penalty for head to head colusions but, IT IS APART OF THE GAME. I am not just wondering this because of the Harrison hit because Steelers Safety Ryan Clark is known throughout the league for hitting head first.

If people do not like the helmet to helmet hits then they should not play the game. This goes with quarterbacks as well. When somebody goes to tackle a quarterback they now are not allowed to hit them in the head, or the lower body. So when there is a 260 lb linebacker running full speed at the QB the last thing he is thinking is how not to hit him illegally. If QB's are not allowed to be hit in certain areas then pretty soon the NFL should change the rule to where if a QB is touched during a play then that means he is down and he cannot continue the play.

 I understand player safety but all the players on the field understand what they are doing. All of them know that they might be hit in the head. If someone does not like it then take up another sport.

Does anyone else have an opinion?