What's with all the physical stuff? Did anyone read Dilmah's link?
There are women who can pass the most rigorous tests that men are ever given, but they should not be put in an intense combat situation with men. Men are generally wired to be attracted to women, which can impair judgment. Fix it with training? Yeah, whatever... maybe. Can you be sure that the training will hold under all possible stressful situations? As that "Women in the Armed Forces" paper said, maybe, but we'd have to get some empirical data, and that means some people will die.
So yeah, it's sexist. But it ought to be, since sex is the fundamental difference here. And it has nothing to do with what women can or cannot do, but how the relationship between a man and a woman is different from that between two men. I suppose you could quantify and actively correct for that, but I suspect that the "correction" would just be pulling women from the front lines.
However, as modern militaries start incorporating more automation and unmanned gizmos, that will open up even more non-front-line positions. Even today, most killing is done from afar, not face-to-face.
EDIT: Where's iamzack?