It's not sexist, and there were a lot of women who felt it was improper for them to be able to vote since they couldn't be drafted. They felt it was an inequality since they didn't risk as much as men with regard to citizenship.

However, I think in a free society we can make exceptions here and there so as many people as possible get to vote, including women. But I do agree that women vote in highly emotional, erratic ways that can be as stupid as "he's attractive I'm voting for him." (Obama)

But we get the bad and the good with freedom. My wife is awesome and votes conservative.