Suppose we stipulate that he is a "racist" (a 20th century neologism in search of a falsifiable definition).
Suppose we further stipulate that he is a white supremacist. Let's even throw in that he is a "Nazi".
If all those things are true, are you willing to execute him even if he is innocent?
That he is a Nazi is not open to debate. He openly self identifies as such. Nazis are enemies of the United States and everything we as a country stand for. He should be shot or hanged on that basis alone.