I would argue that instead of approved nonconformity it is polite nonconformity that is tolerated. Some people self-censor out of fear of disagreement downvotes, but I see all kinds of opinions and that is why I come here. I also think we see what we want in a lot of dialog. Either folks look for opposition and find it or they seek out likeminded opinions and find that too. Its not that there is a central culture here, it is that there are so many differing opinions that you can perceive the site however you choose.