The inside-the-law approach that works to some limited extent is public community rejection. Things like large groups showing up and standing with their back to the Nazis.
The method that has historically stopped Nazis like this involves getting some level of police cooperation and beating them up
Isn’t it very illegal to be one in Germany? Shouldn’t the police be arresting them?
There are certain symbols (like the Swastika) that are illegal, but just believing you are a superior race isn’t against the law.
When I hear nazis I just assume they are doing the salute and are using the symbols.