Unlike McCartney I don't believe directors are at fault for putting violence in movies. Our society is at fault for allowing itself to unravel to the extent that it has. The fact that more people want to watch these violent scenarios is merely a reflection of where movie realism is resonating with the real world. It is difficult not to believe that the world is tipping ever closer to a world war scenario, along with many other bleak possibilities, including pandemic flu, hunger shortages and worldwide social disorder (riots, etc.). While the average person might call these imaginations "doomsday," the truth is that subconsciously it is neither illogical nor farfetched given the rapid declines in world economics.
"The Dark Knight" embodies a mythos that resonates with many: that there is a growing craziness and disorder that is threatening to break loose. We all sense now that criminal elements (or terrorism) are becoming harder to contain.