How do Shane and Fletcher pervert justice?

Fletcher abuses the letter of the laws of entitlement for settling land. He rules with violence in order to protect his unjust little frontier fiefdom.

Shane also operates outside the law, killing when he has to. While these killings may very well be described as self-defense, that is only actual defense in a court of law. Shane never faces judicial processing to clear acquit himself of wrongdoing. The question then is whether Shane is violating justice just like Fletcher, even if not to the same degree. The answer is that while the rules of law applied to small settlements on the frontier, the process was an evolving on in which most of those settlements had first to go through a period in which lawlessness was the price to pay for bringing civilized law and order.