I do think there is too much pressure on managers these days. Sure, United have lost an FA Cup game. But let's just look for a second - they won their Champions League group comfortably, they're within a few points of 4th place. It's not Fergie dominance, but it's by no means a disaster season. I felt the same about the Spurs manager when he was sacked last month. This is completely different from when many of us were calling for Wenger's head after several seasons of mediocrity.
Football needs to shed this short-termism. That Wenger has been manager at his present club longer than all the other managers combined suggests that there is a serious problem with patiance.