Definition of nationalism
1 : loyalty and devotion to a nation; especially : a sense of national consciousness (see consciousness 1c) exalting one nation above all others and placing primary emphasis on promotion of its culture and interests as opposed to those of other nations or supranational groups Intense nationalism was one of the causes of the war.
nationalists come is all flavors and colors but the same ideology within the same group - i would venture most FReepers are nationalists by definition
Supremacists on the other hand are all the same color and ideology within that group ie all white, all black etc.
The difficulties come up because
So you've got people saying "Cultural enrichment is good, cultural appropriation is bad." "Evangelical is good, fundamentalist is bad." "Patriotism is good, nationalism is bad." Or "Conservative is good, alt-right is bad."
It's hard to pin down what people really mean by it. And once the MSM contaminates a word ("Alt-right = KKK") it's pretty hard to decontaminate it.