Honestly, we can go on about historical accuracy or whathaveyou, but this film's worst crime is just generally kind of dull. It so perfectly recreates the sort of banal, Ken Burns
-wannabe documentary style that I saw so often in school that I want to fall asleep just watching it. They are really, seriously, devoted to the bit, and the effects used to make pieces of film look dated or grainy works wonderfully. I'd almost admire the craftsmanship of it if they didn't so completely fail to do anything interesting with the form. It's not a parody, it's a spot-on recreation that happens to be about a ludicrous topic.
The narrative they use it to build isn't particularly compelling, either. After the dozenth warping of history to get across the "Southern people are backwards racist yokels" idea it's hard not to get the point and wonder if the film has anything more to say. And it does—if you stick around to the end, you'll find out that politicians are hypocrites. Shock.
There's no nuance here, no higher aspiration than dropping anvils and appropriating styles. Hell, the jokes aren't even funny. There is absolutely nothing even remotely engaging here, save for a quick bit at the end where we find out that the racist advertisements are for real products still being sold today. Perhaps they should've made a documentary about that if they wanted to use this style so badly. At least then this thing would have a decent shot at being compelling.