Some researchers argue that autonomous weapons would commit fewer battlefield atrocities than human beings [...]
No, it's just that if an autonomous weapon does it, it would be more difficult to call it an "atrocity". If a dozen villagers are killed because of a minefield that some idiot decided should go near where they live, the only reason you can't call that a "massacre" is that there was no human making the targeting decision.
In the 1920s, there were some who argued that aerial bombing would be more humane because they could be far more precise than field artillery, hitting only the target that you want to hit. Look how well that worked out.