What's the problem, refs admit to seeing something and completely screwing up... thus they should be fired and competent referee's employed, or they say they didn't see something and the FA give out a completely fair and deserved punishment to a player.
The alternative is, let refs screw up with no punishment and let players get away with nasty elbows(and other things) on the pitch.
Fact is, not only should Aguero get a three game ban he should absolutely have been sent off during that game, at a time West Ham were playing well, were back to 2-1 and then City would have been down to 10 men. As it is, Aguero stayed on while taking West Ham's best defender out of the game. Woeful refereeing led to a monumental swing in the games momentum by allowing Aguero to get away with an elbow that injured another player.
The "the ref saw it so we can't do anything" rule, is and was always completely pathetic. Somehow a ref trying to defend himself is trying to make it sound like a big problem that people told him to say he didn't see it... yes, they were protecting you from your own incompetence you utter cretin. Still completely blind, you've just outed the guys trying to save you throughout your career.
Is there any suggestion that refs were told to say this, so FA could review something and unfairly punish people? No, this is about reviewing bad calls and giving at least part of the correct punishment.