I think the ref thought McGregor kicked him. It could still probably be a red just for moving his knee towards him but I doubt it would have been given.
Agreed the palace player should of had a straight red for the tackle on Elmo, took him out with studs showing and then studded Mac
The intent was there. That is enough. Sadly the game has gone soft. It was not even a booking at one time. Blame FIFA - UEFA and our muppets at the FA. Pointless. We have Steve Harper so let Alam McGregor stew over his rush of blood.