They do have the First Amendment right to march and wave their flags around. Now, if all major political parties quickly denounced them and the police treated them as the potential threats that they are, then their “peaceful marches” would be ridiculed and they would be driven back into the shadows.

The bigger problem isn’t that they have a First Amendment right to march. It’s that one of the two major political parties watches them match and says “these guys have some good ideas.” Instead of being driven into the shadows of society, they are being given positons of power. And we’ve seen what happens when Nazis are given power.