Who knew that Erectile Dysfunction would be the key to saving the world?
Also a few notes:
-A video of youtuber giving himself a castration would not be allowed on youtube
-A parasite that kills its host faster than it can reproduce is evolutionary unfit for obvious reasons. It's the problem of super mutants in the original Fallout in that they will only last a generation before dying out eventually. What most likely would occur here would be a cross-species virus (not parasite as parasite would easily be detectable and removable) that changes what proteins are encoded so that when sex horomones and certain parts of the brain are stimulated, the body codes for different proteins that cause this.
-Do homosexuals just exist to transmit the condition in terms of the parasite? They can't breed or expel it
-Also just because people can't have sex doesn't mean that they can't have other ways of reproduction. Potential solutions would include a lobotomy that removes the parts of the brain responsible for sexual regulation, artificial insemination and test-tube babies, and using stem cells to artificially grow gamete-producing cells to inseminate indefinitely.