Lol all those dummies out there who don't know that SJW (meaning Social Justice Warrior) is reddit's catch-all term for anyone who believes there is social inequality that needs to be corrected, from "tumblr feminists" - a term meaning "young women who frequent tumblr.com and parrot a lot of feminist buzzwords (patriarchy, triggers, colonialism, male tears, etc.) without fully understanding what they mean" and actual radfems (radical feminists - a small group of feminists who produce most of the hateful speech associated with feminism) to anyone who has a more liberal standpoint regarding gender or racial politics than the average redditor.
The term (and reddit's opinion of it) mostly stems from the TumblrInAction sub which collects the worst instances of tumblr social activism (actually mostly troll accounts, but TiA has a somewhat McCarthyist view of SJWs - if it looks even a little like a real SJW, it is serious and bad) for redditors to mock and also internalize.

Haha what nimrod wouldn't already know that, though. What a turnip.