Noone decides that, because that's not the metric. The metric is whether the party is antidemocratic. As we know from history, sometimes people do vote for antidemocratic parties. But back in 1946 it was decided that no antidemocratic parties shall be allowed anymore, no matter how much support they gain.

Most people do NOT vote for them though, we're talking about 30% at most, and the other 70% are definitely not supporting anything close to the afd

> who decides when its not in the people best interest? Oh right, not the people

Damn right it isn't, because for most of them it is against their own interests. They vote out of emotion.

>Because who decides when its not in the people best interest? Oh right, not the people since they clearly voted for them for a reason.

In Germany we have laws to ban parties that work against our constitution, exactly because of what happened in Weimar. The AfD is classified as confirmed right-wing extremist in five states. Starting a ban process is more than justified. The process is not arbitrary. Only the Bundestag, Bundesrat or government can apply, and the Constitutional Court decides after checking if the conditions are met. Also, just because a majority votes for something doesn’t make it right.