The fact is that there are a lot people who do think "women/men want" when they hear someone saying "women/men want", and don't understand that these aren't just statistical trends. And I'm pretty sure that this ends up causing considerable damage. We should whatever we can to avoid strenghtening such views.

And while you may be right that the average commenter will recognize the difference even without it being explicitly stated, I wouldn't be so sure about the average reader. Note that lukeprog has stated that the article is also aimed towards people who don't usually read LW. A random person who gets the link to this article from his Facebook feed is a lot more likely to take such claims literally than someone who has read through every post on LW.

Also, I do feel like there are tendencies towards such over-generalization even among active LW commenters. For instance, there was one case of a commenter acting condescendingly towards people he thought were carrying out preferences that were suboptimal for their sex. (Or so my memory claims: when I went to look up the details, I noticed that the relevant comments had been deleted, so I can only link to my rebuttal.)