The "law enforcement gangs" we saw featured both genders. Quite possibly, the same would be true of the rape gangs, regardless of the fact that the males would predominantly handle the penetration aspect of the violence. Domination through violence would appear to be a preferred lifestyle on Turkana IV, and it would certainly be in the interests of the females to be active participants on the winning side.
In an anarchy-driven community, lack of willing partners would hardly be a feature in the statistics, dynamics or politics of rape. And the rape gangs would only go by that name because of the most notorious part of what they were doing, even though the bulk of their operations would involve beating up people, thrashing and/or stealing their property, leaving messages from the boss, and making offers that could not be refused.
It was stated in Unification that Vulcan possessed "Vulcan Defense Ships," suggesting they had their own military organization separate from Starfleet.
Or at least there were ships stationed at Vulcan ready to offer defense, either permanently, or then during the events.