I'm not sure that's what they meant - any group of people shares certain beliefs and values, and those beliefs differ from another group's. Values and beliefs influence our communication style as well.
Further, on an anonymous discussion board, the risks of things like "jumping to conclusions" [not what I would call "less contrarian"] are much lower than in real life, where your reputation as a human is on the line.
Anonymous message boards have points, gotta post what people want to hear for upvotes that give that self-validating dopamine hit when you check your score and it's higher than ever.
Further, on an anonymous discussion board, the risks of things like "jumping to conclusions" [not what I would call "less contrarian"] are much lower than in real life, where your reputation as a human is on the line.