Much of the film's content contains footage from the Vietnam War and protests in the US, both of which contain bloody images which are very disturbing.
In Vietnam, there are at least a dozen war scenes where soldiers, women, and children are sometimes seen bloodied, missing arms or legs, and usually running around with blood around them in the midst of gunfire. There are a couple close up shots of people's injuries, but most of these scenes are not very close up, while they are violent and sometimes gorey.
In the scenes of protest in the US, mobs are seen storming the streets, breaking into buildings, and running people over. There is at least a few scenes of police/guards beating people, and blood is shown as many of the scenes are real footage.
While there certainly have been more violent and bloody movies, the fact that much of the violence in this film is real footage makes the war and beating scenes very horrific and tough to watch.