Slash by definition is about gay sex. You may have been confused because Zoe Rayne has some thoughts about this topic on her site . Yes, a lot of writers say this. True for some pairings, not for others. The name Mary Sue predates slash, and the MS phenomenon is more of a problem in gen and het stories.
Poor writing is a lot of it.
Wesley Eugene Crusher, who was invented by Eugene Wesley Roddenberry. Sources for this story rejected interview requests, asked for anonymity, or asked that their testimony be erased after the fact. They fear retribution from the networks for their poaching. That's not why they didn't want to talk to you. But Austin Bunn and Brill's would do well to wonder why David Plotz and Slate found their sources to be so much more outgoing.