1) Countries are really big. There are multiple layers of sub-community, providing for much more diversity even in a country that isn't about diversity. LW is multiple orders of magnitude smaller than Britain even with lurkers counted, and if we only count the regulars, the same can be said of magical Britain.

2) Countries don't have a specific purpose. Websites often do (including this one, used in the example). On a website, simply going off-topic badly can be a bannable offense (not here, yes). A country trying to do that is farcical.

3) The example given above, that I was responding to, was about someone who was let in to LW, did some bad things, and was banned. This is the equivalent of exile. It was targeted and in response to an existing wrong. It was not done proactively for a broad category of people who had not done anything wrong.

4) Speaking of those people not doing anything wrong, "don't, won't, or can't accept [the community's norms]" might be a legitimate reason, but it was not the criterion applied in the example, even approximately.