Todd Alcott says that the confusion raised by the film is because it has a four-act structure, not the standard three-act we are so familiar with. And (this is my reaction to that) given that we are so familiar with the alternative, this is like dissonance, or cubism. It is difficult to untangle 'they did something wrong' with 'they did something unfamiliar'. And just as dissonance proves we understand music, the uneasiness around this film proves we understand the structure of drama. Alcott's opinion is that the 4-act messiness of the plot is a faithful reflection of the irresolvable problem of violence:
By creating a dramatic, crisis-resolving "solution" in a third act confrontation, the Coens would be saying, in one way or another, that there is a solution to our national violence -- either Moss would somehow turn the tables on Chigurh (which would imply that the answer to violence is more violence), or Bell would step in and save the day (which would imply that adherence to law and order is the solution), or else Chigurh would mow them all down and walk off into the sunset with the money (which would imply that we're fucked). But there is no solution to the problem ... and that is the point
I would say it is more about the problem of living in a world that will kill you. A killer thinks he has out manoeuvred death, by becoming death, and killing all who look on him. But then, what's to stop him, invisible, being knocked over by a car? This reminds me of the plight of the invisible people in Christopher Priest's novel The Glamour. The heroes, of various types, make various moves against evil: to come after it, to avoid facing it, to refuse to negotiate, to try to negotiate. It doesn't matter that they are sane, or brave, or wise, they have to give everything up, and only dumb luck or ill-luck makes any difference in the end.
Here is an excellent comment added to one of those reviews:
In the movie, Chigurh asks Wells, 'If the rule you followed brought you to this, of what use was the rule?' In the book, he then asks, 'How does a man decide in what order to abandon his life?' This one question said it all for me and we can see how each major character has this question put to him or her in this story
Reference: review by screen writer todd alcott parts one two and three
ETA and four.
ETA screenplay here