Unjustified Ending of The Proposition

If Captain Stanley hadn't held Mikey (despite believing him innocent) as leverage in order to get Charlie to kill Arthur, then Mikey wouldn't have been in a position to be flogged. Further, Captain Stanley had extorted Charlie to assassinate Arthur, and if it wasn't done by Christmas, Mikey would be hung. That makes three good reasons to kill Stanley - falsely imprisoning Mikey, threatening to kill Mikey, and trying to get Charlie to kill Arthur. Captain Stanley is ultimately responsible for everything that happened after the raid at the beginning of the movie. Besides, Arthur is a sadistic rapist murderer, so we shouldn't expect justice to come from his hands. Justice comes from Charlie, who stops the rape of Martha and kills his own brother Arthur.

Full synopsis of movie

At first I was thrown by the ending, and didn't find it satisfying. I thought about it for two whole days, and then concluded that it could not have ended in any other way. It is clear throughout the film that Charlie is questioning the ways of his brother Arthur, and ultimately decides that the wayward life of the bushranger is what led Mikey to be killed. He decides to draw the line to this path, perhaps thinks it best to make something of his life, and in the process saves Stanley and Martha by killing Arthur and his sidekick.

I think a key piece is missing here. Based on the events as they occur:

• Arthur Burns only knows what Charlie tells him about the situation (Mikey will be hung on Christmas).
• Charlie Burns only knows the situation as it stands at the time he departs from the shootout at the beginning of the film.
• Up until Fletcher shows, Stanley is the one in charge and is the one who imprisons Mikey.
• Fletcher does not appear in the film prior to Charlie's departure, and was not involved in the decision to hang Mikey, release Charlie, nor offer the pardons (he says as much to Cpt. Stanley before the flogging).
• When Arthur and Charlie free Mikey, they then become aware that he has been beaten near to death, leading them to believe Cpt. Stanley to have changed the terms of the agreement.
• The Burns gang only knows that Mikey was killed in Stanley's custody and that Stanley sent Charlie to assassinate Arthur.

The key point being, the only member of Burn's gang who knows Fletcher was ultimately responsible is Mikey, who is shown to be unconscious and dying. All of their knowledge is based on old information, but given their criminal disposition and the decision Charlie ultimately makes, Arthur would take it out on Stanley for the part he actually played, not just what they believe him to have done.