Why? The majority of people arguing that it's not important are people who aren't actually affected by it, while people who are affected by lack of representation in some way tend to think it is important. Do you think that's a coincidence?
I think that it is a generalization, pure and simple and a pretty insulting one at that. Just because someone says that the representation of gender in generic enemies isn't an important issue with them in no ways means they feel fully included in any media. An over weight person may feel excluded in representation in media, but finds generic enemies a pretty small and unimportant area.
I have explained before that I certainly don't feel as though my body type is represented, yet I don't find the lack of generic enemies an important issue either, at least not personally. So yeah, to say, "You don't know what it's like, so how can you understand?" is dismissive and insulting, imo. Yet, it's pretty much an accepted rebuttal.
@BabyFratelli
I don't find it insulting that people think women kill in real life or that women kill in video games. I just think there is a better arguments for the inclusion of women other than the fact we can kill stuff too. That is already pretty much established in Bioware games. I know that it came from the fact some people were saying men are just factually stronger than women, but it seems like using the fact that women kill in real life should be the reason they belong on the battlefield "stooping to that level". Women should be included on the battlefield in Thedas because it's established lore. In battle scenes both in the beginning and end of DA:O, there were just as many women marching to battle. Women are seen as equals in Fereldan because Bioware thought it was important to do so. It makes sense that they would join their fellow men in arms to protect those they love, the land they love and the way of life they love--not because they can lop off a head as good as any man, but because they have the same desire for life, protection and honor as men and have as much to lose if the battle is lost.