Parties in Germany can be banned if, according to the behaviour of the party of their supporters, the party aims to undermine the free, democratic, constitutional order or the existence of the state. Finding that this is the case requires a judgement of the Federal supreme court (Art. 21 GG).
- In the past, the Communist Party of Germany has been banned. Their members reorganized as the German Communist Party, taking care to keep certain objectionable sentences out of their manifesto. The German Communist Party was not banned, but their active members were removed from civil service positions. After the fall of Communism, information came to light that might, in hindsight, have justified a ban of the DKP.
- Two attempts were made to ban the National Democratic Party of Germany, which would meet the example you ask for. The first attempt was rejected by the supreme court because there were so many police informers in the party leadership that it smacked of entrapment. The informers were removed, and the second attempt was partially rejected by the supreme court because the party was found so insignificant by that time that banning it would be disproportional.
- Finally, there was the Socialist Imperial Party, which was more Reich than socialist. It was banned 70 years ago for being too close to Nazi ideology.
A party as you describe it would, objectively, meet the conditions above. All that leaves is to prove it to the satisfaction of the court. The case law from the second NPD case adds another condition, political significance.