I agree that there is some group think at HN, but it is significantly better than most other sites. I believe it's impossible not to have group think as society is conditioned to favour certain beliefs and values, particularly through media, law and education.

As an example, I dislike prejudice and believe in a level playing field. This often puts me at odds with Political Correctness and feminism (eg. I disagree that sexism is a male behaviour (eg. The use of the term misogyny to reenforce this belief) and I condemn sexism by anyone). About 50% of the time I am modded down on HN. Challenging sexism from a feminist a guaranteed mod down at The Verge and a near certainty of being modded down at Ars Technica.

So, I consider HN to be more open minded than almost all other forums, save one. Many users on this other forum are mindful of the PC trap and discourage sexist terms like misogynist (instead of the more balanced, less political term - sexist)