I had an interchange the day before Scalise was shot with some west coast liberal who insisted that the reason Hitler came to power was because of an obsession with the rule of law in Weimar Republic. She was completely unaware of the existence of paramilitary groups in post-WWI Germany. She was arguing that progressives need to start using violence against fringe elements of the right in the US. The irony was incredible.
You said you recognize it because you've read so much European history (and obviously you have), but it doesn't take half of the education you've had to recognize what's going on here. This is really, really simple stuff. The Freikorps are not obscure.
Another great example of how fragile Democracy can be. The funny thing about Weimar is will all its handicaps it was finally succeeding before the Great Depression began and poor economic policies screwed it and the world over.
Happily the US institution is much more robust. But it still amazes me that people think violence is ok in our politics. Unless you're rebelling from England it is pretty much not ok to solve your problems using violence.