While there has been an attempt to revise the narrative of the Confederate States of America to a story of state’s rights, the fact of the matter is that succession from the Union was because of slavery. At the time of succession, those in the lead made no bones about this fact—they explicitly presented this as their prime motivation. This is not to deny that there were other motivations, such as concerns about state’s rights and economic factors. As such, the Confederacy’s moral foundation was slavery. This entails a rejection of the principle that all men are created equal, a rejection of the notion of liberty, and an abandonment of the idea that the legitimacy of government rests on the consent of the governed. In short, the Confederacy was an explicit rejection of core stated values of the United States.
While the Confederacy lost the war and the union was reformed, its values survived and are now explicitly manifested in the alt-right. After all, it is no coincidence that the alt-right has been marching in defense of Confederate monuments and often makes use of Confederate flags. They are, after all, aware of the moral foundations of their movement. Or, rather, immoral foundations.
While the value system of the Confederacy embraced white supremacy and accepted slavery as a moral good, it did not accept genocide. That is, the Confederacy advocated enslaving blacks rather than exterminating them. Extermination was, of course, something the Nazis embraced.
As is well known, the Nazis took over the German state and plunged the world into war. Like the Confederate states, the Nazis embraced the idea of white supremacy and rejected equality and liberty. The Nazis also made extensive use of slave labor. Unlike the Confederate states, the Nazis infamously engaged in a systematic effort to exterminate those they regarded as inferior. This does mark a moral distinction between the Confederate States of America and Nazi Germany. This is, however, a distinction between degrees of evil.
While the Nazis are generally regarded by most Americans as the paradigm of evil, many in the alt-right embrace their values and some do so explicitly and openly, identifying as neo-Nazis. Some do make the claim that they do not want to exterminate what they regard as other races; they profess a desire to have racially pure states. So, for example, some in the alt-right support Israel on the grounds that they see it as a Jewish state. In their ideal world, each state would be racially pure. This is why the alt-right is sometimes also referred to as the white nationalists. The desire to have pure states can be seen as morally better than the desire to exterminate others, but this is also a distinction in evils rather than a distinction between good and bad.
Based on the above, the modern alt-right is the inheritor of both the Confederate States of America and Nazi Germany. While this might seem to be merely a matter of historic interest, it does have some important implications. One of these is that it provides grounds that the members of the alt-right should be regarded as on par with members or supporters of ISIS or other such enemy foreign terrorist groups. This is in contrast with regarding the alt-right as being entirely domestic.
Those who join or support Isis (and other such groups) are regarded as different from domestic hate groups. This is because ISIS (and other such groups) are foreign and are effectively at war with the United States. This applies even when the ISIS supporter is an American who lives in America. This perceived difference has numerous consequences, including legal ones. It also has consequences for free speech—while advocating the goals and values of ISIS in the United States would be regarded as a threat worthy of a response from the state, the alt-right is generally seen as being protected by the right to free speech. This is nicely illustrated by the fact that the alt-right can get permits to march in the United States, while ISIS supporters cannot. One can imagine the response if ISIS supporters did apply for permit or engaged in a march.
While some hate groups can be regarded as truly domestic in that they are not associated with foreign organizations engaged in war with the United States, the alt-right cannot make this claim. At least they cannot to the degree they are connected to the Confederate States of America and the Nazis. Both are foreign powers at war with the United States. As such, the alt-right should be regarded as on par with other groups that affiliate themselves with foreign groups engaged in war with the United States.
The easy and obvious reply is that both the Confederacy and the Nazis were defeated and no longer exist. On the one hand, this is true. The Confederacy was destroyed and the succeeding states rejoined the United States. The Nazis were defeated and while Germany still exists, it is not controlled by the Nazis. On the other hand, the Confederacy and the Nazis do persist in the form of various groups that preserve their values and ideology—including the alt-right. To use the obvious analogy, even if all territory is reclaimed from ISIS and it is effectively defeated as a state, this does not entail that ISIS will be gone. It will persist as long as it has supporters and presumably the United States would not switch to a policy of tolerating ISIS members and supporters simply because ISIS no longer has territory.
The same should hold true for those supporting or claiming membership in the Confederacy or the Nazis—they are supporters of foreign powers that are enemies of the United States and are thus on par with ISIS supporters and members in terms of being agents of the enemy. This is not to say that the alt-right is morally equivalent to ISIS in terms of its actions. On the whole, ISIS is indisputably worse. But, what matters in this context, is the expression of allegiance to the values and goals of a foreign enemy—something ISIS supporters and alt-right members who embrace the Confederacy or Nazis have in common.