You're right about one thing, though: the Nazis are a domestic problem. A domestic terrorist problem. Oh, if only we had a place where we could send people who form armed mobs for the purpose of frightening a large portion of the populace. Maybe made of concrete and steel, with bars on each room. Too bad we don't have places like that scattered around like jacks.
Is it naive to think that that's what jails are for? Or is it excessive to stop considering the ongoing and longstanding use of the state as a tool of oppression "abuse" and start considering the possibility that oppression is actually the state's purpose?
The state is a tool; it is not the state that is a problem, it is the people using it that are the issue. Ideally, the state exists to enforce the social contract: to protect society as a whole (in the form of law and order, as well as a military presence), to provide for the common good (education, health care, etc), and to provide the upkeep for public utilities (roads, rails, and bridges, as well as public utilities like water and power).
The problem oftentimes lies in the first part of the contract, the protection of society at large. We see this in the increased militarization of the police, giving them access to military-grade hardware without the requisite training and experience needed to know
when it should be used for the greatest overall effect. The police, themselves, are easily the largest (and most commonly used) tool for the systemic oppression of the underclass and minorities, but that is
not their purpose. Their purpose is to, as they say, "protect and serve." In a more honest, less idiotically corrupt society, that would mean
everyone. As it is, the people with the money can buy their way out of receiving their just punishment (so...what happened to all them bankers what almost obliterated our economy about a decade back?) while poor people and minorities are abused by a system that is fundamentally rigged against them. That, combined with the shocking lack of oversight when it comes to psychologically vetting our potential law enforcement personnel, makes for a perfect storm of a tool that can be easily abused.
However, ideally, people like neo-Nazis, skinheads, radical "militias," and so on would be put behind bars for either actively committing crimes, aiding and abetting known criminals, or plotting to commit crimes and acts of domestic terrorism. These people are a threat to a large number of people; to deal with that threat, such people ought to be contained in a secured place where they are monitored and kept away from society at large.
But, who's going to arrest a white man when there's plenty of unarmed black teenagers out there just
begging to be gunned down, amirite?