Except there are overt differences between mostly female and mostly male brains.

For example:
http://www.doctorhugo.org/brain4.html
http://www.medicaleducationonline.or...d=46&Itemid=69
http://www.mc.vanderbilt.edu/reporte...x.html?ID=4717
http://health.howstuffworks.com/men-...nt-brains1.htm

Now to move slightly past that point. Brain structure is not a binary thing. You do not find people that have perfect male or perfect female brains. It just doesn't happen. Thus, it is absurd to try to classify any specific trait as 100% male or 100% female. Some are socialized into us and many are there from the beginning. However, no one possesses a brain that structurally is perfectly one gender or the other. Further, most societal conventions about gender roles are not arbitrary. They are usually generalization about what most people of that gender will enjoy or traits most of them exhibit. This is of course not always the case but the vast majority of people of a gender will exhibit some if not a majority of the expected traits even without socialization. The entire argument that being male or female is simply an attitude that can be changed is demonstrably false. I mean you couldn't really look at a persons mental performance and brain structure and definitively say male or female but you could get an idea as to if they would identify to a more masculine or more feminine gender stereotype. Gender of course not being a binary thing but a spectrum of ideas this is not altogether unexpected.

edit:
The comparison is valid because transgender like homosexuality can be, or is entirely no one is sure quite yet, a brain structure issue. If we decide its ok to berate and drug transgenders into fitting in than its a very small direct hop to doing the exact same thing to homosexuals.

The true cause of homosexuality is still being debated somewhat, yes, but do you agree that homosexuals are homosexual not so by choice, but that they just are? If so, then what is so much different about this?

Sexuality exists on a continuum. We have:
*Men who are attracted to men
*Women who are attracted to women
*Individuals of both sexes who are attracted to individuals of both sexes
*Guys who are attracted to chicks with dicks. Look up the Kathoy from Thailand or futunari(not actually real, more of a fetish present in hentai publications) from Japan.

biological sex is also not a black and white. You get males, you get females, and you get a whole lot in between, i.e. intersexed people. These are people who are born with either:
*Both sets of genitalia: hermaphrodites, very rare and I do not know of a case where someone was born with both sets functional.
*Ambiguous genitalia: a sex organ larger than a clitoris but smaller than a penis, usually the doctors decide a sex to "assign" the infant within the first week of its birth, sometimes without consulting the parents, and the decision normally defaults in assignment to female (since it is easier to create a vagina than it is to grow a penis). Or it boils down to the doctor in charge saying "well, I think it looks like a ______.
*People like Caster Semenaya, who has been at the center of some olympic controversy over her sex lately. Supposedly, she has female genitalia but was born with what amount to internal testicles instead of ovaries.

Gender identity is similar, and related to both. There ARE gender differences brain structures and how it functions, and if there are females born with internal testicles then is it really such a stretch that there are males born with feminized brains?

Edit: wow that took a lot longer than I thought to write, or you people are just magic and can type just by thinking at your computers.

Edit Mark. II: I think I am saying much the same thing as SithDarth, but he is saying it much more cogently than I am able to at the moment.

It means something is different about their biology. Wether that is wrong in a social sense is more up to society than science.

There's actually an interesting evolutionary theory about homosexuality. I wont go in to detail, since homosexuality isn't really the main subject, but basically the theory gives homosexuality an explanation in evolutionary terms. I'll try to find a link later.

Psychological delusion is biological fact.

thus he is a dillusional boy. Sex is a very definative and obvious fact. Male human is one with male sexual organs, penis and testicules. Thats the definition of male, he has male sexual organs, he is male. His personal opinion does not alter reality. Someone might run around claiming to be Elvis, just because they truely believe it doesn't make it true. If they get extensive surgery to look like Elvis that doesn't make it true. For a less extreme situation someone might dye their hair blonde and insist they are a blonde in a burnets body, that doesn't change what their natural hair color is, it just gives the outward appearance that it is blonde.

Before it gets to that hermaphrodites are their own class, and plastic surgery does not grant you different sex organs. It merely creates an artificial approximation of the appearance of those organs. They are purely cosmetic. Until someone can create functioning organs and alter their DNA, sex change opperation remains in fact just incredibly extensive plastic surgery.

Similarly, ignoring all the proven scientific evidence of different natural operational mechanisms between male and female brains that Sithdarth posted and continuing on like you know what you're talking about doesn't alter reality, either.

Sex and gender aren't the same thing, the former being the physical aspect while the latter is the hard-coded neural programming part. The two do not always match up, and many years of research and experience in the matter by trained professionals have shown that augmenting the neural to fit the physical is impossible while augmenting the physical to fit the neural is not, and attempting the former is altogether incredibly dangerous for the mental health of the subject.

The whole thing just plain isn't as simple as "boys have a penis, girls have a vagina."

The definition of sex actually includes two things: primary sexual traits (sexual organs) and secondary sexual traits (breasts, body hair etc. AND personality).

It looks like this thread is between a rock and an Aerozord place so I am gonna go ahead and tie this off.