Moral relativism is not a justification for criminal actions. A mercy killing is still a homocide isn't it?

What did they put "Dr. Death" in jail for. They put him in jail for breaking the law. Even though his "clients" wished for him to kill them. There is no justification for killing, or any other war crimes, based upon moral relativism, such as "they were slave owners, or they were rebels, or secess, so they deserved what they got".

For example, John Brown was then and is now still a Murderer. No matter what his motivations were. He had no authority to establish his owns law. Nor take the judgement of law into his own hands. And any others who followed his example, gave him support, or refuge, or praised his actions were equally guilty also.