Murder could be removed as a concept from our minds.
Just as anyone would never try to move forward by turning in a circle. Murder could itself be framed as a paradox that can't achieve anything in particular.
One could think of moving forward by rotating in place, but ultimately there is no feasible action that can achieve forward movement on a sphere from even rotation of the human body on its surface. And those unfeasible that do give some effect are beyond our mental or physical capacity.
Similarly our understanding of the world could one day abstract to a level where conflict or murder isn't simply reprehensible but makes no actionable sense as a whole, gives no result.
The two most obvious ways would be to make all other people permanent in the full effect of their existence, or to make them invisible by restricting some or all of the ways of how they affect others. Other people could be this feature of mental landscape (mindscape) in the distance that can be seen, but can never be reached or altered.
It's probably much easier to moderate all interaction through a virtual medium, so that it loses all physical consequences. The desired consequences could be reached by a concession from both parties and effected separately in their own shielded instances of reality. Any two people conceding to enter a single physical reality from their virtual medium would most likely come with a bunch of protocols and restrictions, that could only be removed with consent, force would be a non-factor, sophisticated algorithms would spot coercion, etc.
Though since all physical interactions could be transferred over distance or simulated using a safe virtual copy of other people's whole being, there would be no need for contact. Removing someone from one's friend list would be more effective than killing, they could be completely erased from the carefully controlled information feed.
