I don't like "social justice warrior" as a name, but that's what the internet calls the angry identitarians who love to mob, threaten, and dox in the name of social justice. So, for the sake of this guide, I'll use it.
I first noticed identitarians in the community in 2005. Their beliefs about race had been formed by Critical Race Theory; their beliefs about gender came from what Christina Hoff Sommers calls gender feminism, which I think could be more precisely called identitarian feminism. Their first major "kerfuffles"—flamewars that swept from blog to blog—came in 2008 with The Outing of Zathlazip and the Hounding of William Sanders.
In the first case, a young woman who wrote as Zathlazip made a post at a site called Something Awful that made fun of people at Wiscon. In return, she was doxed and mobbed online. Offline, someone went into her office and left a threat which terrified her so much that she went to the police.
In the second, William Sanders, a Cherokee author, made comments about Islamist terrorists that were interpreted as Islamophobic. In return, he was mobbed and threatened, and the International Conference on the Fantastic in the Arts (ICFA) withdrew its invitation for him to be its Guest of Honor.
A year later, Racefail 09 began when two white writers, Jay Lake and Elizabeth Bear, wrote blog posts saying that people should research other cultures when writing about them. Their explanations were first found wanting by Coffeeandink, a white SJW. The scifi internet quickly exploded for several months. What continues to amuse me is that if you use dictionary definitions, none of the people involved were racists—people like Vox Day ignored that fight or watched it from the sidelines.
Two American Indian "fails" quickly followed: Patricia C. Wrede was denounced for writing an alternate history in which humans never went to the American continents before the European voyages of the Middle Ages—this was interpreted as "erasing" American Indians.
A year later, Neil Gaiman was denounced for saying, in response to a question about the setting for The Graveyard Book, “The great thing about having an English cemetery is I could go back a very, very, very long way. And in America, you go back 250 years (in a cemetery), and then suddenly you’ve got a few dead Indians, and then you don’t have anybody at all, unless you decide to set it up in Maine or somewhere and sneak in some Vikings.” The phrase "dead Indians" was called racist, and the mention of the fact that American Indians didn't bury their dead in cemeteries was interpreted as a claim that there were few or no American Indians.
In 2010, Elizabeth Moon was uninvited as a WisCon Guest of Honor after writing a blog post that was interpreted as Islamophobic. People like N. K. Jemisin vowed to boycott the convention if Moon stayed its GoH, even though the co-GoH was Nisi Shawl, a black woman who had never said anything to upset fandom's warriors.
In 2012, Victoria Foyt's Save the Pearls, a book about a white woman overcoming her racism and falling in love with a black man, was denounced as racist. When Marvin Kaye, editor of Weird Tales, defended the story, he was attacked. Ann Vandermeer, his co-editor, resigned. His defense was removed from Weird Tales' web site, and he cancelled his plan to publish an excerpt from the novel.
In 2013, several kerfuffles arose regarding SFWA, the Science Fiction and Fantasy Writers of America. One was over a cover of the SFWA Bulletin featuring a swordswoman in a chainmail bikini. Another was over the reminiscences of Mike Resnick and Barry Malzberg, who said that one of the field's first female editors, Beatrice Mahaffey, was attractive as well as capable. The uproar resulted in the resignation of the Bulletin's editor, Jean Rabe.
In 2014, one of the most vicious SJWs, a blogger whose many pseudonyms included Requires Hate, was exposed as a professional writer, Benjanun Sriduangkaew. Moderate SJWs denounced her while extremists defended her in a kerfuffle reminiscent of the clash between Girondists and Jacobins.
And now, we have whatever the uproar over the Sad Puppies will be called. I hope it won't be Hugogate, but the people who try to connect it to Gamergate make me fear it may be. If you want to know much too much about SJWs in SciFi and outside it, last year I updated old blog posts in a book that's free at Amazon and Smashwords: How To Make A Social Justice Warrior.
ETA: For the record, I understand the outrage in some of these cases. What Zathlazip did was juvenile, Sanders' initial comments did seem Islamophobic out of context, I was one of the first to criticize Moon for her simplistic take on Muslim immigrants, Save the Pearls is naively written (based on the little I read), and chainmail bikinis have seemed stupid to me ever since I saw the first one in the '70s. But in all these cases, the mob reaction was vicious: none of their victims deserved what they got. The greatest difference between the original practitioners of social justice and the people who get called SJWs now is the first group believed in treating everyone with love and respect; the second believes, as all bullies do, in hurting their targets so badly that what they perceive as the social contract will never be broken again.