Top misconceptions of Theory of Evolution you had to deal with

[God of Mr. Hanky]

I'm not sure that this was ever floated as being an observation, or that such a gene existed...simply describing a superficially counterintuitive scenario, and how known mechanisms could play out in in creating such a scenario.

Human males, gay or straight, don't have a habit of killing off other males offspring in order to replace them with their own.

They don't now. Do chimp males kill each other in a contest for their females? If not, maybe they did 4 mya, and they still do kill for the position of Alpha Male. But the utility of having gays in the family may not have been so much a question of ape killing ape, nor so with early humans - gays are just as good at helping care for the young and protecting them against predators, and can be trusted not to have eyes for Brother's wives. Conversely, wives don't get to use gays to cheat on the family patriarch.