I took it as metaphorical rather than literal, since I couldn't imagine how Rainbow Dash would actually rape a larger creature; presumably she defeated it badly in some kind of aerial combat or race.
since I couldn't imagine how Rainbow Dash would actually rape a larger creature
The established character of Rainbow Dash notwithstanding, it's certainly physically possible. For example, it could happen if the larger creature consumed a significant quantity of alcohol or other drugs and was therefore incapacitated. Blackmail or other some other kind of threat could also work. Not wanting to hurt her could also make it harder to fight back. Or it could simply have been Not What It Looks Like.
For the past two months, I've been writing, and posting, roughly two thousand words a day of "Myou've Gotta be Kidding Me", a story set in a "My Little Pony: Friendship is Magic" fanfic universe, "Chess Game of the Gods". Outside of the sheer NaNoWriMo-like exercise of pushing out near-daily chapters, I've also been trying to keep in mind the various principles I've learned from Yudkowsky and LessWrong, and to try to present them in a way that people who like reading MLP fanfics might be able to appreciate.
I've just come to something of a minor climax with chapter 60, and while I'll definitely be continuing the story, this seems like a good time to mention it here, for whatever feedback and constructive criticism anyone cares to offer.