I don't think this rioting, violence, and general unrest should be compared to the Brown Shirts. Groups engaging in "antagonism and murder towards people they perceived as evil" are not uncommon in history. An analogy to the Nazis in the 30s seems out of place because, as you say, of everything that the Nazis did after the 30s.
If you want to talk to about ideologues, people for whom the ends justify the means, people who are willing to engage in violence and destruction for ideological goals, then you can make a comparison here. You can put the Brown Shirts in this category, you can put current rioters in this category, you can put a large number of historical groups in this category, and I think this categorization is fair. (Note that sometimes this violence may even be justified).
But why pick the Nazis in particular for your comparison? Comparing this group or that group to the Nazis is almost always rhetorical trick precisely because of the Holocaust. Why not pick some other group in history that used violence to pursue its ideological goals but didn't boil over into a genocide? The answer is that, if you picked another group, the rhetorical power of the comparison would be lost. But it would be a more honest comparison.