Are they? Bonnie and Clyde's ending is one of the most violent I've ever seen. If that scene were in Kill Bill, they'd put it in black and white like they did with half the movie.
Again, watch more movies from the 1920s, if you can find them. And don't give me that excuse of "They didn't know what was acceptable yet!"
Tons of nudity, graphic violence, porn, smoking, drinking, all that stuff.