Funny. When the State ends the life of somebody, we say "it was JUSTICE". When I go and stab somebody then it's "murder". Or not. It depends on what the lawmakers at the time agree murder is, no?
In principle I agree that you have to draw the line somewhere, but that is mostly completely disconnected from reality. It's just a matter of bureaucratic feasibility. So, please, tell me where you get this unwavering certainty from, that lets you see "pretty clearly" where the line needs to be drawn. Or I could be dishonest and assume you are just making stuff up as you go or quoting directly from your Bible.
The lawmakers need to tell you what murder is, you don't understand yourself? Are you being serious or intellectually dishonest? Value judgments are subjective, and of course they are influenced by culture. That doesn't mean what a barbarian believes is as valid as what a civilized person believes.