If "popular ideas" == Neonazis trying to overthrow the German constitutional order, then yes, that is the appropriate response.
There's no awards to be won for coddling fascists. The protections of a free society cannot be extended by those trying to extinguish it.
> When our enemies say: well, we gave you the freedom of opinion back then- yeah, you gave it to us, that's in no way evidence that we should return the favor! Your stupidity shall not be contagious! That you granted it to us is evidence of how dumb you are!
And I understand that this might seem like hyperbole to the less-informed American reading this.
It is for their benefit I have translated a few quotes from leading AfD members so they can paint their own picture what those "ideas I don't like" are: https://news.ycombinator.com/item?id=49536747