Thanks for the suggestions, everyone!
When I notified airbnb of this, they initially told me that they would cancel the reservations and refund the money to these predatory guests. Not only was I expecting a lot of money from this booking, but I also sunk money, time, and effort into getting my place ready for them. When I told them that the money was more important to me than my safety (I didn't really have to interact with these men, since I could just stay at my boyfriend's place, so this wasn't terribly high stakes), airbnb said that they could cancel the reservation and keep their money after all.
Air bnb offered some unsavory solutions: canceling with the guests by notifying them that they wouldn't tolerate sexual assualt. If they'd done that, then these men would have had the opportunity to trash my place. I wound up notifying the police, which was surprisingly alarming because five cop cars descended on my apartment with sirens and everything. They removed the men from my apartment but, shockingly, said they couldn't arrest the one who sexually assaulted me. Then they condescended to me and informed my boyfriend that it was ill-advised to "let" me greet these men alone. Perhaps their energies would be better focused on considering that it's actually illegal (certainly ill-advised and morally repulsive) to sexually assault a person.
This victim-blaming culture has got to go.
For anyone who finds themselves in this situation in the future, I would recommend contacting the authorities and airbnb simultaneously. It seems like airbnb has no satisfactory system in place to deal with this type of (dangerous) situation.