While I'm not sure what part of the world you're in, I know that a large portion of the slashdot readership resides in the USA. And here (possibly other places, but I can only reliably talk about here), male-to-female transsexuals are generally offended by the term "shemale". They seem to prefer either "trans-women", "MtF" or just "women". That may explain your -1 troll.
That said, it seems humorous to complain about how trans-erasure has kept people from acknowledging male-to-female transsexuals while also ignoring female-to-male transsexuals. At least trans-women are noticed because they are sexualized - trans-men seem almost wholly ignored in the populace.
But to answer your question more directly, the reason nobody talked about them in *this* article is because they are not a lucrative target market for advertisements. The homosexual male community is not targeted for advertisement because they are so numerous, but because the retail and marketing world believes that gay males spend a lot of money and, more importantly, influence the fashions and tastes of the heterosexual people surrounding them. Clothing stores see gay men as trend setters, so they believe that getting gay men to adopt their clothes will lead the heterosexual people to follow. Because of rampant discrimination and erasure, trans people are not perceived as having the same trend-setting appeal.