Oh, we aren't. The history books will have to "find" gays that did great things. These could be people who did great things that we already knew were great (Abraham Lincoln), or they will just make up great things that were done by not-so-great people who were allegedly gay (Oscar Wilde). Or take a person who is largely presumed gay and puff his achievements as hard as possible (Oscar Wilde again).
Expect to see a lot of Oscar Wilde.