I know, but how come we have now people from AfD in parliament in Berlin who openly gave interviews and public talks where they proclaimed the state and existing system has to be rebooted/abolished completely? Have they walked the thin line right at the edge that it was barely legal?

Do you think Verfassungsschutz (state dpt enlisted to protect the Constitution, and basically a spy/police agency) decided it's better to let them in for now and continue spying on them? Past events with informants and NSU do not fill me with confidence that Verfassungsschutz is doing their declared job.

It's clear why people vote for them, since they play the FUD strategy well, but I'm confused there hasn't been a concerted effort to expose them and their agenda.

Any insight?

I'm not German but my understanding is that AfD has walked the line. NPD on the other hand didn't but the courts said they were too insignificant to be banned, which may have increased the legal hurdle in the future which might not be great. Here's a good analysis of it [1].

[1] https://www.lawfareblog.com/renaissance-militant-democracy

As I remember the main reason given for not being able to ban them was that too many of their important members were undercover agents from Verfassungsschutz so it wasn't clear where the prohibitable ideas came from.

This was the case during the first banning attempt in 2003. This was fixed during the second one but that was declined this year due to the NPD's relative irrelevancy.

One thing to keep in mind is that the AfD has considerably moved to the right since the 2013 election. While the "old" AfD under Bernd Lucke clearly stayed within constitutional boundaries, the rise of unconstitutional opinions within the party is a relatively new phenomenon.

And it's made thinly veiled racist agenda mass acceptable as seen in this year's CSU (and to some extent CDU) communications. I'm scared a little, to be honest, though I continue to trust the checks and balances of the system supported by the rational minds of the greater population.

Well, of course they're against it, because it's a tool that enables the establishment to silence the AfD.

People say that, and yet the yearly neo-Nazi street marches in Germany are bigger than anything that US has seen so far.

What exactly are you refering to?

In US, Charlottesville, of course.

In Germany, well, just google for "Germany neo-Nazi march".