Communities have existed since the dawn of man and CoCs weren't necessary to keep idiots away. When someone is an idiot, you don't need a set of rules to identify that he's an idiot, and to have a basis to kick him out. If you 1) can't identify idiots or 2) can't kick out idiots, then you have a dysfunctional community or no teeth. CoCs can't fix a community or make you grow teeth.

Communities have had published standards of conduct since the bronze age.

> you don't need a set of rules to identify that he's an idiot, and to have a basis to kick him out

afaik, a code doesn't exist because of an inability to identify or to (attempt to) exclude a person.