https://en.wikipedia.org/wiki/Socialist_Reich_Party

The party claimed Chancellor Konrad Adenauer was an American puppet and that Grand Admiral Karl Dönitz was the last legitimate President of the German Reich, as he had been appointed by Adolf Hitler. It denied the existence of the Holocaust, claimed that the United States built the gas ovens of the Dachau concentration camp after the Second World War and that films of concentration camps were faked. […] It demanded the re-annexation of the former eastern territories of Germany and a “solution of the Jewish question”.

TL;DR: If you’re openly a nazi party in 1952 you might get banned.

EDIT: Also helps if you’re willing to ally with the soviets in 1952, it seems.

said that he would “show the Russians the way to the Rhine”

Wehrhafte Demokratie macht BRRRRRRRRRRRRRRRRRRRRRRRRRR

There allready is precedent for banning parties. History and current events both show that people are fully ready to vote fascists into power. And also, you know what’s one of the big reasons so many people vote for fascists? Fascist propaganda. Banning fascist parties will help have fewer fascist citizens around (at least after a while).