I believe the horse collar rule is b.s. and touching the QB and hand slapping on O-Lineman is baloney.s
The horse collar rule was instituted because Roy Williams was hurting a receiver like every game. Torn hamstrings, etc. The body is just not supposed to be loaded like that.
THe problem is it is called poorly. Grabbing a man's collar and falling on his legs while he is running full speed forward most certainly is dangerous.