Right, so, basically, it doesn't.
There was so much to complain about, I split my comments into this 10-min read which I followed up a 29-min read that may have a bit more info on your question.
In short:
The way Roberts accounts for trans people is the "sex realist" aka "gender critical" way: that we're all really our originally assigned sex/gender.
So, under his schema, trans lesbians are straight men, and trans gay men are straight women.
Regarding trans lesbians: Since his worldview is that all men are predatory/exploitative/violent/appropriative, especially against women, and that being trans is an elaborate deception (of oneself and of others), of course he says that trans lesbians are straight men who must be exceptionally terrible toward women. That's the only way he can slot the existence of trans lesbians into his worldview. His argument is of course unsound, so I hesitate to say he "draws" a "conclusion," but anyway, that's where he ends up.
Regarding trans gay men: The "sex realist" aka "gender-critical" schema typically ignores us because it can't account for our existence nor does it have a plan for how we should be treated. (The anti-trans people don't really have a plan for what to "do about" trans men overall, as officially they don't think we're men, but neither do they want male-appearing people in women's bathrooms, so the existence of us trans men crashes their argument against trans women — and regarding the fact that some of us trans men are attracted to men, we break the reductive anti-trans trope that all trans men are essentially butch lesbians.) Roberts says we trans gay men are “one of the very little discussed areas of ‘trans’," which is "much less prevalent and much less known” [than trans lesbians]. He says there are "very few" trans gay men. He describes us only through how he imagines cis gay men would react to our existence: with "an embarrassed, amused, shuffling don’t-know-where-to-look reaction," with "pity" as "the dominant response." Basically he's saying that we gay trans men would be interesting to him if we were already "discussed" by cis people, but because we are "very little discussed," we aren't very "known" and therefore our very existence is "less prevalent," and so he will continue not to discuss us or even to know of us. He essentially recommends that, if a cis gay man did ever encounter a trans gay man, "pity" would be a reasonable response. The end.
