I didn't try to claim that you had to have a chromosome difference to be trans, merely that the research tends to show that it is caused in the womb. Studies of transsexuals show that their brains have the characteristics of the gender that they claim to be. Studies done on other animals have shown that introducing the hormone of the sex opposite the offspring given at a particular stage of development causes them to be transsexual. We've discovered that in polluted areas of coastline, where there are high levels of fertilizers and other estrogenic chemicals, have caused transsexual animals to be born.
Perhaps there are some that aren't actually transsexual today and that is something the medical community needs to do a proper job of weeding out. The fact remains that there does seem to be an actual birth defect, one that is difficult to make while the patient is alive (it basically requires an autopsy of the brain, scans alone aren't accurate enough), and that therapy has not shown the ability to fix. I'll also point out that the way many transsexuals are treated today, that making them feel like a "man in a dress" or similar, obviously causes suicide issues in those that successfully transition -- and that ending as a "man in a dress" is far less likely if treatment (such as puberty blockers and hormones) occurs earlier, such as during early teen years.
I'm not advocating anything here, merely pointing out that it is a tough issue but one that, from the research of the last few decades clearly appears to have a real, physical cause (is essentially a birth defect), and that starting current treatments later is less successful. I'll also agree we need better treatments but, short of much better types of surgery or the ability to actually change a persons physical sex, I'm unclear where that better treatment will come from.