The issue is, that we're not really justified in many of these situations. And when we are, we can only enter those countries with little power - not necessarily all of those that are committing atrocities.
I also wonder if we've created so much conflict that there's no easy way out now.
The point is it doesn't matter who takes up the helm in this country. The body count is never going to be 0. So when do we declare victory? When it's less than 10000 50000? When we burn the country to the ground and build a better one that only kills 20000 a year? It's never going to be acceptable.