I said this in another post...i think it really boils down to a lack of terminology. It doesn't really seem like the gay/straight dichotomy gives us the right tools to really discuss it.
I'm not sure if a lot of tgirls want to be considered a third sex. I can't really comment on it besides that it makes a little sense to me, especially considering those girls who want to live as women but don't want to get SRS (i'm not wrong in thinking there are girls like this, right?).
It seems clear to me that an attraction to tgirls is something different than an attraction to males...just what to call it, I have no idea. Queer, maybe?