Not true. In some cultures in history the killing of another was a sign of strength and the killer's rightful due.
What if murdering someone resulted in saving many lives? Some would view it as the moral choice.
Our troops kill people in the hopes of protecting our country. It's not labelled as murder, but the result is the same. Many people find this acceptable moral grounds.
My point. You missed it. Killing is
not the same as murder, i.e. the two terms mean different things. The term murder is a specifically-defined kind of killing, which, by definition, is extra-legal and immoral. So when you use the term "Murder" you implicitly condemn the act as immoral.
Soldiers killing on a battlefield is not murder, though it is killing. One contemporary example is the killing of a Taliban IED emplacer instead of arresting him. In that case, it's not murder, because he is an enemy combatant.
As for murdering someone to save lives, well, that's still an immoral choice, but you'd just have to live with that on your conscience. I'd love to hear a reasonable example of how that situation might come to pass, however.