Why should horse collars not be allowed? If it is the only way a defender can tackle a guy then he should be allowed to do it.
They say long hair is a part of the jersey and that is dangerous as well if someone gets pulled by their locks head first to the ground.
Run faster or realize your leg may be broken if you get collared. Injuries happen. Deal with the concussions or don't play.
If the league wants to protect itself and protect players then ban guys after x amounts of concussions or something. I have no problem with that.
Kickoffs will soon be eliminated as well as punt returns and I can envision at some point in the future where a QB wears red and can only be touched unless he crosses the line of scrimmage.