Don't know what excuse they used but for me it was a tame backing-down. It was a cynical attempt to bring down a player with studs down his ankle, preventing a possible breakaway, so a red was correct - imo.
To clarify, if the ref had given a yellow I’d have disagreed, but accepted it as being the ref's subjective opinion. His opinion was that it was a red, and that should have been accepted too as far as I'm concerned.
In other words, stick with the on-field decision, unless it is unequivocally wrong.
Gordon's was a red card, but don't be surprised if they come up with some mealy-mouthed excuse to downgrade it.