Few people understand this film
This is a film about weak men. Pretty much all the men in the film are weak in one way or another, but David takes center stage as the weakest of them all. The film is ostensibly about him, and his weakness.
It also goes along with the theory that David is the true villain of the film. Everything bad that happens could have been prevented by him taking the proper actions at the proper times. He could have managed the lazy workers and nothing else happens. Or he could have confronted them harshly about the dead cat, and nothing else happens. He could have acted properly around his wife, and she would not have felt the need to 'act out' and solicit attention from the other men, and the rape would have been avoided. Even the death of the little girl at the hands of the village idiot could have been prevented by David, as he was aware of the girl's inappropriate behaviour and could have taken action.
Once things spiral out of control, like a true weak man, David eventually explodes with the rage he has bottled up for so long and over-reacts, killing 5 men and beating his wife in the process. He is no hero, he has not 'saved the day' at the end. At the end he is lost and alone.
The only thing I couldn't understand about the film is how a man like David could end up with a woman like Amy in the first place - it seems absolutely impossible. But I've come to realize that Peckinpah intentionally contrived this situation in order to highlight what does happen when such forces meet (the beautiful self absorbed woman and the weakling geek). In fact the whole film could be considered a metaphor for that.