Birth of a Nation is kind of a guilty pleasure, just because you cannot believe what you are seeing on screen, and cannot help but take pleasure in laughing at the movie. It's a guilty pleasure and entertaining, just cause the content is so mindblowing. If that makes sense?
It's a propaganda movie, but it's well done propaganda movie. But a lot of propaganda movies come out all the time really. Even Rambo: First Blood Part II, is about how all Americans are good and how the Vietnamese army is evil, and in conspiracy with the evil megalomaniac Soviets, even though they were not.
So if people can find that kind of propaganda entertaining, perhaps Birth of a Nation, maybe can be taken on the same level, to a degree? But even if it can't and goes too far, you still cannot believe what you are seeing and it comes off as funny in my opinion.