For a more hands-on online approach, there are also more direct consequences to goose-stepping to the tune of the bad guys of WWII. A Twitter campaign is currently in the process of identifying the marchers in order to name and shame them in the eyes of the world. As you can imagine, calling out a Nazi in front of their schools and jobs is a fairly effective strategy that sends a fairly solid message: If you're participating in a Nazi activity and dare to peek out of that moist mud pit you generally revel in, you will be tracked down and publicly branded. And your day shift manager at Big Wally's Hot Dogs And Tires is not going to be happy.
There's a flipside to this, though. Although the internet isn't as horrible as Nazis, it still is pretty awful. Instead of doing the sane thing and actually checking the available images from Charlottesville to see if there were any people they know and can reliably recognize, many people have taken to internet sleuthing, which in this case means lazily image searching the faces and screaming wolf at the first result. Please don't ever do that. It's generally considered impolite to implicate innocent people just because an algorithm decides "These two people have mustaches. SWITCH TO OFFENSE MODE." Besides, finding out that you kind of look like a Nazi is a pretty s****y thing to discover on a lazy Tuesday, even if it isn't followed by an inevitable torrent of doxxing.