I agree with you that there’s no need to pretend fascists have a valid point. But those who would reason with them fail to understand that fascists are beyond caring whether they have a valid point or not. They are simply determined to have things their way. While we try to educate fascists about where they’re mistaken, they will smirk and load their guns. To them it’s funny that others are so stuck on argument when you can just use violence to get what you want. They see this attachment to argument as weakness and stupidity, and they know what to do with the weak and stupid.

That said, whether banning the party would help depends on how committed their voters are to the fascist cause, and I’m not familiar with the scene in Germany. Maybe if there are many who are just disgruntled but not particularly committed, putting obstacles in the party’s way could buy time to turn them away. But people get sucked in quickly because fascist groups know how to make people feel they belong, pander to their egos, and rapidly program their prejudices while persuading them everyone else is lying. It has cultish aspects, so there has to be a plan for how to deprogram people from a cult.