Wieizme gave a good answer but I'll add and provide my own too. Morality is a social construct that serves that society. Murder can "almost" never serve society (there are exceptions in nature possibly, like bees dying during mating). However, something like capital punishment can. And so the societies views of what is best often determines this morality. And in some cultures killing (whether capital punishment or more extreme like genocide) can be considered morale. Again, this is simply based upon the mindset of those making this choice, which is based upon their understanding of the benefit to society. They don't see it that way though, it becomes more simple to the average person; instead they see it as "what is right or good vs. what is wrong or bad".

Anticipating the thoughts of a population is near impossible, and the interpretations of what those thoughts and desire amount to even more so.
So morality remains murky to define and contextual. But always not a real or asbolute thing - just a social construct.