Having only a passing familiarity with Slate Star Codex, I can't claim to have much knowledge of the context here. However, using information gleaned from this comment alone, I would say that polite steelmanning is probably the default reaction to a lot of things as far as LW readers are concerned (this is obviously and sadly untrue outside of these circles), and that if feminism, social justice, and Tumblr were reacted to with genuine disgust, something probably happened to justify that disgust. If I'm wrong about this, feel free to inform me.