Every community has a set of shared assumptions and a particular viewpoint, this is pretty much axiomatic given the definition of the term. Most forum systems on the net are unable to deliver much nuance in terms of expressing this viewpoint, so it is easy to perceive "groupthink" when the bulk of the community disagrees with you. Where things get interesting/contentious is when people who share community view A assume everyone else agrees with B and get indignant or defensive when they discover that this view is not shared. There is nothing about "hackers" or startups or other standard topics of this community that necessitates a unique viewpoint, so why assume the rest of the community is going to tolerate large divergence from a standardized norm? Too much input from "unique" viewpoints usually leads to chaos, and that seems to be one thing of which the community has a low tolerance.