I'll take the bait.

I am going to go out on a limb here and assume that by "Nazi" you mean people who are not politically left, but I will address it as if you meant actual Nazis.

I think anyone has the right to choose to believe whatever they want, even if that means they believe things that are undoubtedly wrong, such as Nazi beliefs. That of course does not absolve them of the consequences of laws they might violate. Certainly such a person would have the right to tell other people about what they believe, but this would be counterbalanced by other people having the right to just not listen to them. If someone else has the right to speak that doesn't mean you are required to listen to them, you could choose to just walk away entirely.

If you think about smoking a cigarette, I would imagine you would agree that smoking is very, very bad for your health. However, anyone that wants to has the right to smoke. But if they smoke in an area that is designated a "no smoking area," then they would be required to leave. Likewise if a person wants to believe Nazi ideals, as much as I personally believe that would be a very bad choice, they have the right to choose to be wrong. However, if they act upon their beliefs which leads to them breaking laws, then they should be held accountable for that. I am not an expert in Nazi beliefs or ideals, but I would imagine that them taking action on their beliefs would very likely break laws in pretty much every country. And rightfully so, people should not be allowed to just say one race is superior or the only one deserving of living and then actually take action on that. I may be wrong but I think it is illegal to have Nazi beliefs in Germany? In which case the law applies and if someone was provably holding such beliefs where it is indeed illegal, then they would absolutely deserve whatever the legal punishment is. To my knowledge, simply believing Nazi beliefs is not illegal in the USA. It might be racist and stupid, but not illegal.