Solve the problem...
Design a nano virus that is injected into a homosexual persons bloodstream, let nanobots attack the impulses of same sex attraction, kill all future homosexual development if need from the day after birth with a homo vaccine.
Too unrealistic? Not one bit at all.
Some day in the future the anti homo virus will be in drinking water the same as fluoride. Homo refugees will find it extremely difficult in the future to avoid the cure.
What could possibly go wrong in this SF scenario?