Violent hits are ok blindsided cheap shots are not ask Darrel Stingly !!
That Tatum-Stingley event was horrid in result and, in line with your proposal, this type of tackling should be cultured out of the game. Still, the rule must have truth on its side. When one player hits perfectly with his shoulder-pads into the sternum, his helmet-head will make secondary contact as an immediate continuum of the action, but doesn't impart the tackling-blow. = that perfect tackle should not be penalized as it is being penalized currently. Ignored in all this is the event where the ball carrier lowers his head to lead with his helmet in 90% of those collisions. ?? Doesn't that natural reflex "spearing" need rules to prevent, to make the game safer ? Preventing the damages of impact in a sport wholly based on hard collisions radically changes football. It's a difficult tampering.
The severity-aftermath of an injury does not determine that the hit was dirty. Football has dangers : heat stroke at practice, coming down injuring the neck even without being hit, dehydration dangers, etc. Precautions may improve these, but there will always be some.