This Western gives an effort, but the writing is sorely contrived by the mind of someone wanting to accuse the wrong sort of people of being deranged. It smacks of modern dark ages Psychiatry that "mob mentality masses" want to believe, but in fact are opposite of reality.
The "lunatic" of the story just isn't reality based. In fact, the writing of his character is dangerously misleading. Dan Duryea portrays a man who is insane. The reasons given are "silly", and made by idiots who think they understand human behavior.
The story begins with the characters usually designated as identifiable all being massacred in the usual Hollywood contrived way. Hollywood has always been big on this device, although it really became the "cliché" after the mid sixties. But don't be fooled. Even in 1955, when this mess was made, it was still the "formula", not the exception that today's liars like to pretend it was. It was not "risk taking", but "safe" procedure.
Leaving the audience with nothing but hateful characters has always been the Hollywood device to try to make you root for a minor sicko over a major sicko. It does fool the feeble minded, but it won't fool anyone else.
The biggest problem is that Duryea's character is contrived to fit the hate mongering of the writer and director. Only a moron would believe an accountant would dress up in his dead brother's Confederate uniform and become an unexplainable psycho. It looks like someone trying to make a false story to explain something he doesn't want to admit really happened.