A person's gender - more accurately gender identity - is not the same thing as their sex. A person's sex is indeed determined by their chromosomes (although let's not get side-tracked about what sex people with XXY, XYY or other exotic chromosomal combinations might be).
And sure, undergoing hormone therapy for the rest of one's life and even gender reassignment surgery does not change one's chromosomes. However, it is incredibly insensitive to refuse to accept that someone may identify as a gender different from that which they were born as. And it would be insulting if you were to insist on referring to someone as a 'he' when they clearly identify as 'she'. A male transvestite is a man. A male to female transsexual is not, even if they still retain their male genitals. (And what of hermaphrodites, intersex, and neuters?)
I'm sure I don't need to remind you that many people who don't fall into the neat male-female sex binary have suffered discrimination, bullying, and worse throughout their lives. We don't need to contribute to that. I know that the subject here is "just a porn person" and that they are unlikely to read this thread but that doesn't give us free reign to be insensitive to the feelings of other members, some of whom may be transsexuals themselves.
Lastly, this is one single section in our forum which was created due to member requests. Transsexual porn is not gay porn. This is not a fringe view but a widely-accepted niche category of straight porn. Lots of men who consider themselves to be straight enjoy TS porn. Whilst transsexuals are not my nor many people's thing, there is nobody forcing you to click on the links.
Please feel free to continue this discussion but let's do so as informed and considerate people.