Yeah, I have to be honest that I didn't really know how far out there it was when I rented it. I think I'd only first heard of it when I watched the commentary on Forrest Gump and found out that it was used in that film. And the back of the DVD case goes out of its way to be apologetic for the views contained within. I honestly thought that, like a lot of old media repackaged for modern consumption, it was being overly accommodating for fear of offending sensitive people. At most, I thought it would sympathize with the Confederacy and maybe have a few "Steppin Fetchit"-esque characters, so I was quite surprised with what I got. At the time, I didn't know it was originally premiered with the title The Clansman, based on a play and book with the same title. The DVD actually has excerpts from the book, and it's even more graphic and overtly racist in its descriptions if you can believe it.
Obviously the pivotal scene in the film is when the younger sister jumps to her death to avoid the pursuit of "Negro Gus." The book's analogous scene is with a different female character who was ommitted from the film entirely, wherein a group of black men, led by Gus break into the house of this young girl and her mother, and Gus actually does rape the daughter. The next morning, in shame, the mother and daughter hurl themselves from a cliff. After that is a purely ridiculous scene where Dr. Cameron uses a microscope to read the impression of Gus on the dead mother's retina. Didn't they use that tactic in Wild, Wild West?
My guess is that the movies couldn't get away with something so overt, so the end result is actually a bit strange. Gus approaches Flora in a field and asks to marry her. She freaks and runs off, and he gives chase. Amazingly, he's actually given a line where he says, "Don't run. I'm not gonna hurt ya!" Eventually he chases her to the top of a mountain where she threatens to jump if he doesn't back off. He doesn't so she jumps. From a film standpoint, substituting an action-packed chase sequence was probably a more exciting and less threatening sequence than actual rape, but the "menace" of the black man is greatly reduced. Aside from the poor decision to continue to chase her, Gus really didn't do anything wrong. I don't think he ever even touched her, so the fact that he gets lynched for it certainly has a much more sympathetic context for us than Griffith probably intended like VINH said. But who knows?
Like Warbler said, there is something about it. I think I'm actually going to watch it again before I have to return it. I admit that I do find it a bit embarrassing that I brought up the subject and feel that I have to constantly add several, "I am not a racist," disclaimers to anything I write here. Hopefully, at least, I'm not giving the impression that I am, because I certainly am not.
In terms of censorship, though, I am quite impressed and amazed to find that it is readily available at a local Blockbuster to rent. No matter how grisly or out of date the subject matter is, I am strongly opposed to simply pretending something didn't exist. I wouldn't go nearly so far to say that it's a "blot on cinema history." It's quite a marvel in cinema history, and the more I learn about it, the more amazed I am. It was the first film to extensively use telephones in its production (Griffith ran telephone lines underground during battle scenes in order to relay instructions to different groups of actors), it was possibly the first film to utilize motion photography at night, and it's generally considered the first blockbuster in cinema history. I don't think it necessarily implies that everyone who ever saw the film held the same viewpoints that the film expressed, but, like Star Wars 62 years later, it was just something that everybody had to go see. So in all those respects, it is a crowning achievement in cinema history. It just holds a reprehensible and extremely bigoted viewpoint, which I think is a major blot on the film itself, but the film itself isn't a blot on cinema history, if that makes sense.