Birth of a Nation
I...genuinely don't know how to react to this movie. On the one hand, basically invented modern cinematography, and largely holds up today. On the other hand, ridiculously over-the-top racist.
In some sense, it's interesting to watch just to see what kind of tricks movies use to get people emotionally involved, because it's easier to realize you're being tricked by cinematography when you're watching a movie with outrageous political goals (lots and lots of damsel in distress tropes! "The southern white women are in danger, rally the KKK!" Lots of ominous music for northerners, with lighting that casts shadows over their eyes. The black militia is constantly firing rifles into the air at all hours of the day. The KKK is depicted riding on majestic horses, never firing guns into the air. The southerners are shown gaining allies in unexpected places, the enemies are just a mob which already existed or came from elsewhere. "[strike]Han[/strike] Northerners shot first").