The phrase "women and children" is frequently used to highlight the severity of a disaster; for instance, the BBC's Friday article "Afghan Kunar probe accuses Nato" opens with the statement that "65 civilians, including 50 women and children, were killed in a Nato operation."
I cannot conceive of a single non-sexist reason for referring to female casualties in this manner, especially juxtaposed to juvenile casualties. I can accept the viewpoint that causing the death of civilians is more deplorable than causing the deaths of military personnel; though both are terrible, one can argue that a soldier accepts the possibility of violent death when enlisting. I can also accept (and, in fact, do share) the viewpoint that the death of children is particularly tragic, given that children often require the protection and support of adults to survive. Neither of these arguments apply to women.
It is true that, on average, women are a little smaller than men. But this is irrelevant for two reasons: first, some women are larger and stronger than some men. So, if you must single out a sub-population for being smaller, why not actually choose by size? Second, if you haven't noticed, we tend to use guns, not clubs, to kill each other these days; for better or for worse, many modern instruments of destruction may be wielded effectively by anyone.
I am a competent adult woman. I am non-violent, but this is by choice, not necessity. I greatly resent being categorized as helpless and childlike. Stop it.
For a more nuanced discussion of this topic, check out Nadia Hijab's article.