The only video of the play I could find, it cuts in right as Porter's hand is on the arm/shoulder of Frazier. I can't tell if they just got tangled up going to the same place at the same time with Frazier coming from his blind side, or if he grabbed Frazier on purpose as you stated. I would tend to think accident, but if solid video proof shows it was intentional like you said, there is no justification for such action, and in my opinion should result in termination.