Then it becomes a question of definition, who is a Nazi? I don't know any government body I trust enough to not misuse that term to strip uncomfortable people of their rights.
A person self identifying as a Nazi should be treated as a pariah and a threat to society.
A person who has been but are no longer should be welcomed back into society.
A person someone at a desk somewhere classified as a Nazi to strip of rights and humanity should not be persecuted with bo other proof, instead it should be the actions of the individual that should be the basis of judgement.
Just compare to the amount of LGBT people who got branded "communists or communist-associayed" just to prohibit them from being full members of society in America during the red scare, also known as the Lavender Scare