All the Scouse fans moaning about Rafael doing exactly the same thing, if you look at it, he leaves the ground but is not flying in full pelt like Gerrard did and even stayed up after he came out with the ball.
Everyone that I was watching the match with (United, City and 2 Liverpool fans) didn't bat an eyelid when Rafael tackled him but all agreed Gerrard was right to go.
I'm certainly not saying Rafael done the same thing however if Meireles doesn't pull out of the challenge it would have looked 10x worse than it did. Both feet left the floor and he's stamped down on the ball; it was a silly way to tackle and had there been any contact he could have easily found himself in trouble.