Johnson was physically instigated by Finnegan. Finnegan kept jamming Johnson in the facemask. Hands to the face is illegal and did not get called on Finnegan the entire game. There was not and should not have been a suspension on Johnson.
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Seymore on the other hand just staight bitch slapped Rothlisberger without physical instigation, a suspension was warranted. My point being that if someone gets physical with you then you have a right to get physical back.