1. We ban people we don't like. They aren't actually Nazis, but we don't like them so we pretend they are.
2. They go to some other place where we don't yet dominate.
3. Now we assert that everyone in that other place is also a Nazi, because they aren't doing the same thing we're doing.
If the Nazi Bar was really a real concept then every left wing political party in the world would be a Bar and therefore everyone voting for them would be a Nazi. Because, recall, they were the National Socialists, and every left wing party has a whole lot of committed socialists.
Luckily for political harmony, other people don't use this type of reasoning to eliminate their enemies so left and right parties can compete fairly for votes. Which is why it needs to be stamped out amongst those who do use it.