This has bothered me for quite some time. When a defensive player is rushing and hits the offensive player in the face mask (accidentally or on purpose) a flag is thrown for illegal hands to the face. Same when an offensive player does that to a defensive player rushing. I have seen it called on corner backs when they go to jam a receiver and the receiver hits their hands and they come up and hit the receiver in the face mask. So what is the rationale for allowing a runner to stiff arm a defender in the face mask? I know the rules allow for it, but why. If it is a safety issue, then shouldn't it be prohibited for runners as well? Here is a picture (hope it works) that illustrates the point: