It lowers the barrier of entry to use lethal violence and that is not a good thing. A more realistic scenerio is that rich countries will have less reason to seek diplomatic solutions now that the only people doing the dying are the poorer nations they wage war against. Just imagine how many years an all robot military could occupy a nation with no public blowback because of casualties. At that point it's a cost calculation.

Just imagine how this might be applied by powers like the US, Russia, Israel, and China. IMO its a recipe for increased use of force and extended violent occupations. And that's not even getting into the issue of autonomous kill decision capabilities.