Consider, for example; culturally, over a large part of the world, it is considered acceptable for a woman to wear a skirt, but frowned on for a man. As a result, few men wear skirts; if you were to pick a random man and ask for his opinion on wearing a skirt, it is likely that he would not wish to do so. However, if one considers a slightly different culture for a little (for example, the Scottish kilt), one finds a similar garment being worn by many men. So a person's preferences are affected by culture.

So, should we campaign to increase the number of men who wear skirts and the number of women who wear traditional Scottish kilts? Or the number of non-Scottish people who wear kilts? Or the number of Scottish people who wear pants? I don't know, what is the proper PC ideal here?

One means of maintaining such a division, is by creating a further, artificial divide, and using that to widen the gap between the groups. For example, if significantly more men than women own land in a given society, then restricting the ability to vote to landowners will tend to exacerbate any official pro-male bias. (This works the other way around, as well).

I don't think anybody proposed a restriction of voting rights based on the partecipation to LessWrong or yoga classes, thus this seems to be a slippery slope argument.

Please don't take this personally, but trying to "re-educate" people to change their preferences in order to socially engineer an utopian society, is the hallmark of totalitarianism.
I think that, as long as people get along peacefully, it's better to recognize, acknowledge and respect diversity.