The conventional wisdom about "The Birth of a Nation" is that it represents an impressive and innovative display of cinematic skill that was unfortunately wasted on a story that promotes a bizarre and disturbing point of view. While that is certainly true in a general way, it might also be something of an oversimplification.
It really is almost like two different movies. The first part, which takes place in the era before and during the Civil War, contains little objectionable material, and it deserves praise both technically and for the acting. The second part, set in the reconstruction era, contains almost all of the disturbing material, and it also is really not all that great in terms of cinematic quality.
Then also, the degree to which "The Birth of a Nation" may have influenced the development of cinema has very likely been overstated . The controversy that it generated may very well have helped it to remain better known than other films of the era that were equally innovative and/or lavish, or nearly so.
If the movie had ended shortly after the memorable and well-crafted Ford's Theater scene, the anti-war sentiment and similar themes would remain the main focus, since the effects of war on families and individuals is depicted convincingly and thoughtfully. In that case, its occasional lapses would possibly at the worst be called "dated", given the quality of the rest of this part of the movie.
The second half, though, is completely unfortunate in almost every respect. Not only does it promote a distorted viewpoint, but the story becomes labored, and the characters lose their depth and become more one-dimensional. The purely technical side, such as the photography and the use of cross-cutting, might still be good, but much of the rest of it loses its effectiveness.
Perhaps more importantly, it really seems rather difficult to justify the credit that this one film gets in the development of cinema. There had already been numerous feature-length movies, and most of the techniques that Griffith used were also in use by others. He may well have been ahead of the pack in terms of appreciating their possibilities, but that does not mean that cinema would not have developed as it did without this particular movie.
Just as one example, the Italian epic "Cabiria", from the previous year, has the same kind of lavish scale, is quite resourceful in its techniques, and is quite entertaining, without causing so much controversy.
Other early feature-length films also include some creative efforts to adapt film-making techniques to longer running times and more complex stories. Finally, many short features from the pre-Griffith era experimented with the same kinds of techniques that he later would use systematically. There's no denying Griffith's considerable technical skill, but others of the era also deserve some credit, even if they and their works were less controversial, and are now largely forgotten as a result.
