Well, someone has to represent these voters, or they will co-opt another party or put up their own candidate. And the government can’t just keep banning them, or they’ll catch bystanders (“dog-whistles”) and look super illegitimate (when you prosecute people for holding an empty sign, like Russia, you’re the baddie). Already I believe banning the AfD is stupid and would backfire egregiously in a few years at most.

Ultimately, you can’t ban ideas in a democracy, unfortunately even the idea to abolish it. What you can do it make that process harder and slower, so your opponents lose power before they succeed. Or, you know, convince people to drop the idea altogether.