It plays right into the normal=good, abnormal=bad paradigm. We don't want to believe that neo-Nazis or white supremacists could be otherwise "normal." But the fact is, they are. A lot of them look normal and if you saw them shopping in the local supermarket, you wouldn't know how evil they are just by looking at them. But that scares us, doesn't it? We would much rather have them look just as monstrous on the outside as they are on the inside. We would love for all of them to wear "White Power" t-shirts at all times, and some of them do literally wave a flag (a Confederate flag, of course), but many of them know enough to keep a low profile. Yes, Trump ascendance has brought a lot of them out into the light and some of them will stay there, but a lot of them will know enough to go back to keeping a low profile.
The lesson here is to not let that make us complacent. Just because there hasn't been a KKK rally in awhile doesn't mean that they no longer exist. We have to remain constantly vigilant. As I learned in Hebrew school lessons on the Holocaust: Never forget.