The fundamental difference is that one is an economic ideology from which the genocidal ideas can be separated, and the other is a genocidal ideology. National

The fundamental difference is that one is an economic ideology from which the genocidal ideas can be separated, and the other is a genocidal ideology. National socialism is an ideology for which certain types of people cannot exist, and such it is wholly incompatible with modern societies. Compare this to the fact that socialists and communists have been part of peaceful modern political systems. It is not that difficult to draw the line.