I believe that Morality is both absolute and relative, absolute in that there is a universal and timeless morality that we through the passing of time come to learn through (as you suggested before James) evoluton and the development of our conscience and powers of empathy. Meanwhile, while we are journeying toward that 'absolute' morality that exists outside of ourselves and despite ourselves, we use relative morality to guide our actions.
Hence as time goes by, things considered acceptable in the past become unacceptable in the present and more so in the future. We are less barbaric today than we were yesterday.
In cultures where some practices are still barbaric, they are in every sense behind the modern world, in terms of development. So rather than the barbarism being just a cultural norm, it is a difference in development of that particular group of people. In some point in their future they will up to where we are now and also consider the actions of their present barbaric in their future. Such is evolution.
We are as a people evolving towards a higher understanding of our universe and that includes a higher understanding of all life and appreciation for it, especially as we come to learn the true fragility of what we have here.
Some people are closer the the moral truth than others hence the differences in opinions on moral issues. While some depend on relative morals dictated by culture and society and religion, others can see beyond these and form their own moral choices based on a higher set of values that form the absolute moral code.
For the world to live in harmony all cultures thus need to be up to speed in their development both emotionally and developmentally. This is not the case and probably cannot ever be the case. Hence the instability in the world. Meanwhile, while recognising the more barbaric nations among us, we must not be intolerant towards them, afterall their present is merely our past and we were them at one point in our time. We should show them the path rather than 'beating' them into it.