When looking at the pictures and news clips of these "Nazi Sympathizers" I see a crowd of angry young white males. Rightly or wrongly they see themselves as victims, not the members of a privileged white majority. Since school age they have been inundated with how bad white males are (stereotyped). They have been described by society as being rapists, bigots, racists, islamophobic, misogynistic and the all around cause of other peoples troubles.
Of course, for their ancestors, some or all of this is true, but, having to continue to suffer for the sins of their fathers is creating a subset of very angry young white men. We are reaping what we have sown.