Navajoeverclear; My opinion is that human sexuality is on a kind of slidescale, it is not an either/or condition. Males that exibit female behavior and vice-versa can be seen in a many instances, not solely in sexuality. These variations may be subtle or not, however, like in our political views, society has provided/enforced only two dominant catagories. Though Physicaly we are built with one given sex (with the exception of hermaphrodites) Mentaly we may be built with more variation. It is possible these mental differences are a natural counterbalance to overpopulation, thereby necessitating there exixtance in society.
My source is poor, but I seem to remember a pbs/discovery channel special that stated many animals have as high as 10% homosexual members. Furthermore I doubt that all homosexuality is caused by trauma, though it may be a contributing factor for some. Hope this helps