I've just read it through. Some points are well made.
Transgender is about identity.
Being transgender doesn't mean we necessarily have to completely transision to the opposite sex. It doesn't necessarily mean our sexuality will, based upon our birth sex, be gay or straight or anything else. It is simply a need within us to express our identities is ways that are not generally conforming to a norm. It may manifest itself in our appearance or availablity permitting, a total SRS.
LGBS is largely about sex. For some, the identities of those we make love to can be very important. Some partners of those who have come out as transgender have said they cannot deal with what, to them, is a 'homosexual' relationship. That much aside, LGBT is still about sex.
Where I take issue, serious issue with this writer is where I take the same issue with other. Their assertion of some genetic absolute.
They quoting of the XX and XY rules, for example. I doubt many who do this, do so from the point of knowledge. But accept that their motives are largely motivated by ignorance.
The issue is, in reality, considerably more complicated than XX and XY. Those are terms for high school. They are simple to explain and understand.
One of the most feminine young women I have ever seen was, at the age of 15, diagnosed with Androgen insensitivity syndrome. I'm sorry, but the mere detail that she is sterile dosn't make her a man.
That she would be just as sterile as a man should demonstrate that these things are a lot more complicated than can be explained by the teenager's first book on genetics.