To me, Brown just put the brakes on hard and slammed his back into Naismith as 'obstruction with a bit of needle'. There is no elbow, the arm just flails about a bit. No action necessary.
But Naismith's actions are altogether different; kicks out at Hayes erchie when prone on the ground and ridiculous levels of aggression afterwards fall under the 'bringing the game into disrepute' bracket. Just typical Hertz really.