Multiplicity

Fair enough.

I acknowledge that women are vital to the continuation of the species whereas we only really need a few healthy (hopefully oiled and naked) men.

However, I was only using the example of my brother and his girlfriend because (in this way) they are completely different to the normal mode of gender relations. (She also likes to wear pretty skirts ... mind you, so does he.)

The main point I was attempting to make is that you are making a lot of generalisations.

"I am sorry, but it is not for women to say what is the duty of men, any more than it is for men to say what is the duty of women."

And its not for you to say what is the duty of men, anymore than it is not for me to say what is the duty of women.

"Boys do not have to defend girls because of physical differences, but because it is the opinion of men that this is what is right for them to do."

You are assuming that all men hold the same opinion.

"You may consider that the male urge to defend women is a survival trait - not only because dead women cannot bear or raise children, but also because when women fight, they do not tend to take prisoners."

Is there a "male urge" to defend women?

I'm sorry, but all of this still relies on the distinction based on physical differences.

Just because a man has bits dangling between his legs and women don't does not mean that all of the people with dangly bits will think and act in the same way. Nor does it mean that all the people without those bits flopping around will think and act in the same way.
(Forgive my use of "dangling" and "flopping" - it is not meant to be derogatory but is merely an attempt at humour.)

Basically, what I'm pointing out is that everything you are saying seems to be based on the belief that gender is split into neat and pretty dualistic categories.

I disagree, just as (I'm guessing) you would disagree that all multiples fit into neat categories.

You are right. It is unfair. That doesn't mean I'm going to stop fighting it.

:)
--Drizz