Cross dressing can be no more genetic than riding a bicycle or eating spaghetti. How the sexes dress is a historical/cultural phenomenon not a genetic one. The gene/hormonal wash/DES arguments are, IMO, just pseudo-scientific updates of the "devil makes me do it" argument. In my case Confucius has it pretty much nailed except that I don't believe I "interpret cross-dressing as actual contact with a female." For me it is just the fetishization of childhood emasculation trauma. I find it cathartic the same way that some rape victims find it cathartic to fantasize about rape scenarios. I don't really fully understand how that works but I know it does. Compared to some of the other ways I have expressed PTSD, my CD/emasculation fetish is pretty benign.
Either that or Cthulhu makes me do it.