The first LotR fic I ever read, the one that got me into the fandom, was Aragorn & Legolas & Gimli gen. The next fic the author wrote was Aragorn/Legolas. The pile of vitriol that fell on her (in part because I think people thought she was a "safe" writer, so it was betrayal mixed in with anti-slash) made her delete everything and leave the fandom. And she was a well-known, popular writer. That was my eye-opening moment about how nasty the fandom could be.