If you are looking at an incident (As Mariner was) and you see an elbow, you would blow up for a free-kick and send the player off. Mariner was looking at the incident and didn't see anything wrong with the respective challenges. Under FA rules that should be the end of the matter.
It's like saying the ref was looking at a challenge in the penalty box that 90% of people thought was a penalty but the referee doesn't give it. Do you retrospectively award a penalty because the ref was looking at the incident but didn't 'see' the foul. No, because that was his decision based on what he saw and how he interpreted that situation - its the referees judgement, that's what they get paid to do.
This trumped up charge would never had been brought but for the rag infested media. The problem, is that the SKY pundits are so poor and ill informed about the laws governing the game that they thought they had 'caught' our star striker bang to rights. The problem is, under FA rules they haven't because the referee saw the incident and awarded nothing - if you are looking at an incident you can't claim you didn't see it.
You can, often legitimately, claim you didn't see it in its entirety, every detail. Which is what Clattenberg will claim. And it will be impossible for City to prove otherwise