There's no denying he lashed out, the question is which of the following was it:
1) A fuck you have an elbow to the face you ****, clear intent to hit him in the face?
2) A get the fuck off me, shove him away with his arm motion?
Ones a 3 match or more ban, the other could easily be just a 1 match ban as they were reviewing it on it's own as an isolated incident. The only other time Aguero has lashed out like this(well last time was worse) that I can remember is against David Luiz and that was years ago, his temperament is good with the amount of lumps PL defenders regularly try and take out of him(often getting away with it, some in penalty situations).
If it weren't for the fact the ref definitely did see it and didn't think much of it at the time, we wouldn't be able to argue too much with a 1 match ban or perhaps take the 3 match ban a bit less begrudgingly(would have been 1 if it were a rag, they'd have been showing the angle which proves he didn't connect with the elbow to lessen it).