People transition for various reasons, there's lots of people under the trans* umbrella.
Quoteopposite sex organs, then why would it matter if you're not old enough to do anything sexual?
Gender Dysphoria is a medical condition where your brain believes its body should be of the other sex. It's not just about penis and vagina, it's about body hair, muscle mass, voice, etc.
I don't identify as either male or female, but have considered transitioning to male because I feel like I should have a male body. It's not about sex for me, I am actually not really interested in sex much, I just want to be a manly hunk.
QuoteIf the reason for transitioning is more gender role oriented, then shouldn't we be simply focusing more effort on eliminating gender roles?
Yes, I also extremely dislike the social ramifications of being FAAB. Many MAABs extremely dislike the pressure put on men to be strong, manly, etc. Many trans people, along with others in the LGB and feminist community, are actively fighting to end gender discrimination on both sides. However, there's nothing inherently wrong with someone being ultra-femme or a ultra-manly, there's nothing wrong with being a good mixture of both -- we want everyone to have the ability to be what's natural for them.
Now, what is gender exactly?
That definition varies per person. I believe gender is socially constructed, and that people's behaviors are influenced by society, genetics, and hormones. Feminine is stereotypes of females (sweet, caring, weak, emotional, passive-aggressive) and masculine is stereotypes of males (strong, unemotional, bread winners. . .), your gender identity is somewhere on a scale between those two extremes and comes from some genetic/hormonal/societal factors; some people are more towards one end than another, some people are right in the middle and feel "bigender" or "two-spirit" and others feel like they fall outside and are "non-gendered" (or other terms used to describe this).
Others in the trans community though are very adamant that it's not socially constructed but is somehow biological. I don't understand that but that's fine.