The problem with De Gea is he's made himself a target for criticism in the media at least. When he comes for a cross, people are waiting to see if he makes a poor punch or doesn't cleanly get to it. If someone like Cech misses a cross or punches weakly, its just something that he did. If De Gea does the same people already have the narrative written.
De Gea was not a fault for that goal anymore than anyone else. The ball into the box was pretty much undefended, The CB gets beaten, Evra is marking no one, Lennon is allowed to put the ball back in no one is marking Dempsey, no one is on the post. De Gea's weak punch is one in a whole line of **** ups that resulted in a goal. But Evra allowing Lennon to put the ball back in the danger area doesn't sell as many papers a De Gea mistake.
I doubt he will be leaving, he's got plenty to improve upon, but he's not a liability by any stretch of the imagination.