I think many groups develop norms, and enforce them by social stigma or shunning. I don't think, for example, that it would go over well if one showed up for a NAACP meeting in a Klan outfit . . . Humans are very social animals, and generally want approval, so they learn their norms quickly and either conform to them or avoid groups where they don't fit (thus the ridiculous nature of my original example). I don't think you can stop that process from occurring, nor do I think it's desirable to do so. In extreme cases, that type of enforcement of norms can be destructive, as in the cases of suicides of young people over cyberbullying. In the majority of cases, it's an effective way of guiding behavior to keep it acceptable to the peer group. I would not want to live in a world where laws were the only things that controlled human behavior, because politeness can't be legislated, nor can consideration or thoughtfulness or generosity.
So I guess yes, I think it's okay to develop rules and enforce them by the means available for social enforcement, with the caveat that our tools to do that nowadays are far more powerful than they have ever been in the past, and need to be used judiciously. I'm not sure any of us really KNOWS how powerful these tools are, but I think the case that sparked this thread has given a lot of people a fast and sometimes uncomfortable lesson about that.
However, all such social enforcement depends upon the desire of the individual either to be accepted, or to avoid the social penalties for his actions. If someone doesn't care at all whether he is stigmatized or shunned, or even courts that type of penalty, the system breaks down, and that's when you have to have laws or formal regulations to control what people do.