It was Josh Sawyer's idea, George Ziets wrote it. Personally I find straight men writing about a lesbian woman's rape to be quite disgusting and inappropriate.
I don't really see how a gay man would do a better job.
I mean wouldn't a straight guy better understand the whole not wanting to have sex with a man thing?
Well, I won't speak for people I'm not, but from my experience with gay guys and dykes (I'm friends with a few, and I dated a lesbian for a while once, too... long story), I would say that maybe the fact that you think that, suggests what the problem is. Lesbians aren't just guys with lady parts. In a society with defined gender preferences, like the late twentieth/early twenty-first century, the experience of being a marginalised orientation can lead to some fairly complicated feelings towards sex and gender in general. It might well be worse for a gay woman to be raped by a man than it would be for a man - it would certainly be different. I don't really want to start grading rapes from bad to worse: knowing a few people who've experienced them, there are really no "better" rapes.
Also, We don't really know much about the sexual identity politics of the post-apocalypse, beyond how people respond to the cherchez-la-femme perk etc., and that Arcade, Christine, etc. talk openly about their preferences. We don't even know if anyone even identifies as straight or gay. It's implied, but never absolutely determined. For all we know, it's like the world of Firefly, where most people are a little more flexible - the fiends could spend every night in a bunch of drugged-out gender-bending orgies, for all we know. The legion regard women as lesser - maybe they practise the ancient Hellenic attitudes to love, that another man is the better choice for actual (sexual) bonding? The ancient Romans didn't really have their fixed ideas of straigt or gay, either. As Curio said of the real Caesar, he was "omnium mulierum uirum et omnium uirorum mulierem" ("every woman's man, every man's woman"). I love to imagine that while all these little twelve year old gamers are thinking how tough the Legion is, the legionaries "under the tent canvas" are violating every idea they have about what constitutes proper ideas of masculinity. And since Josh Sawyer wrote the legion, and he has a tatt from the Bellum Catilinae, I wouldn't be surprised if that were the case.
Anyway...
In short, it's complicated.
That's all assuming, of course, that you really are a guy. It's the internet, so you could be a hyper-intelligent pan-sexual giraffe for all I know (and if you are, I'm totally cool with that).
Edit: Quote is from Suet. Divus Iulius LII, btw. If any other periti latinae linguae homines in filo sint. And if any of them want to suggest a better word for "comment thread" than filum, you're welcome. What does modern Italian use? Anyone?