The article answers this efficiently:
“What does ‘Nazi’ mean, or signify? Many things, but among them is ‘Kill all Jews.’ This is not an opinion. It’s a call for actions, such as blowing up a synagogue with people inside or murdering 6 million people who are Jews.”
Put another way, I don’t see Atwood calling for banning Nazis per se. She’s calling for doing something about people calling for the extermination of Jews. That is precise and narrow.