who is to say we need any "norms" or "limits"?
Norms, or limits, came about from the drive to survive.
Even animal packs have rules that were created over time through survival. I.e., gorillas know from experience that doing XXX gets them killed. So when another gorilla tries to do that, they go ape shit on them rather than let the one gorilla endanger the entire group. (Pun intended).
Humans have learned over time that the most effective way to survive is in complimentary groups. That is, I can do X, you can do Y, we combine together to do X and Y. As a result of this basic survival instinct, we figured out that to live together we need rules. Otherwise we just get pissed and kill each other.
This law even extends to message boards on the internet. Message boards with no rules are inevitably flooded by spam, hate messages, and invariably fall apart and disappear. Boards with moderation to a certain set of rules tend to engender community, since there is at least a minimum standard of behavior.
For example, a user on many message boards would get banned for telling an immature narcissistic attention whore to fuck off. But no poster here would say that to another, because we have rules that forbid it so it's easier to get along.
*crosses fingers*