Every single Justice System in the World has a range of sentences for even the same kind of killing crime (for example for Murder) and even different crimes for the killing of another human being (such as Murder vs Manslaughter).
So even the various Justice Systems in the World recognize different levels of blame and deserved punishment for different situations where a human being kills another.
Justice Systems, even if containing plenty of unfair or ill-drafted laws, at the high-level encode what Society finds acceptable and unacceptable - you might have some countries with the Death Penalty and others without, and different minimum sentences for Murder across the World, but there isn’t a single Justice Systems in the World with a single fixed sentence for Murder, which would be what matches your “Murder is Murder” position.
Meanwhile your argument on this is “the law makes no difference”. Full, unadulterated, 100% personal opinion of the denialist kind.
Denialism is not Skepticism and it’s the very opposite of “academically inclined” and putting forward and holding a theory entirelly on what you believe without in this entire thread even once putting forward even the most basic piece of supporting evidence that the rest of the World thinks like you (everything has literally been what you think and what you disagree with) is about as anti-academic as it gets.
Granted, for you it is as you say - Murder is Murder - (that’s pretty well established by now).
For everybody else there are only two logical possibilities:
Most other people don’t think like you
Most other people do think like you and the discrepancy between everybody thinking like you but setting some of the most important formal structures in Society in a way which is completelly inconsistent with that, is that everybody else but you is a moron.
Occan’s Razors is a pretty straighforward way to determine which of the two possibilities is the most likely.