Sexual assault and rape sometimes cause long-term trauma which makes having sex unpleasant. People who find sex unpleasant are less likely to do it, and consequently less likely to have children. Assuming controlling sex is one of the most important functions of society, we would expect to see sexual assault and rape institutionally deployed to accomplish this function (kind of horrifying).
Military victory is often followed by the invading army raping the conquered locals. This might be purposeful to decrease the population growth rate of the conquered, allowing to conquerors to gain a population advantage, especially useful if the conflict lasts generations.
Are there other instances of this happening?
Sexual assault causes long-term trauma only sometimes, only under certain conditions (though we have not yet exactly identified those conditions). A society or subculture might be engineered so that people deemed less desirable to breed encounter those trauma-inducing conditions more frequently, and then a background rate of sexual assault, causing trauma in some but not in others, causes the differential rate of having sex and consequently having children. For example (perhaps this is more general than just an example): sexual assault might cause trauma only in people lacking a strong social support network. A strong social support network is granted only to those who abide by the rules and membership requirements of the society or subculture; those who do not are shunned and live as lonely outcasts and suffer traumatic consequences.