If we're going to generalise, then I think it's far more accurate to say that men don't know how to deal with the level of emotional input that women expect them to put into a relationship, whereas women can't deal with the lack of emotional input that men put into relationships.
That's a rather paraphrased way to put what I mean, but I've just woken up and am struggling with words right now. I would argue that men don't understand women but at least we try. From my experiences, women don't even try to understand men. It goes without saying that this is a very black and white way to view the emotional differences between the sexes, and it certainly doesn't apply to everyone. Some men have a higher emotional input than their female counterparts, but seeing as the majority of women seem to be more in touch with their emotional side (the lack of it on mens' behalf could be sociological, the way we are genetically programmed, or a myriad of other reasons) I'd wager that those men are in the minority.
My evidence for this claim is fairly simple. How often do you hear or read about about (told from a womans' perspective) that "her man" doesn't "do enough" in the relationship? And I'm not talking about doing the dishes or putting the toilet seat down, I mean actively engaging in communication ("he never calls me!" [this could be as it appears, or it could mean "he doesn't do what I want when I click my fingers." It's down to the personality of the woman in question as to what hides between the lines, if anything]) amongst other things.
Naturally this comes down to the individual (everyone is different after all. Not all women are going to complain that their boyfriend would rather play GTA two evenings in a row instead of doing something together), how close the couple are, how clingy/needy either of them are, the circumstances of the relationship, etc.
Put it this way: my claim is quite the generalisation. It doesn't really hold much ground due to the subjective nature of the topic. So if mine is worth dismissing, why wouldn't yours be?
tl;dr: I've just woken up and have been mashing the keyboard while figuring out what I want for breakfast, there's little in this post worth noting.