Robots do not act cruelly unless specifically instructed. I agree that in theory, killbots fighting killbots could lead to very clean wars. The problem is that

Robots do not act cruelly unless specifically instructed. I agree that in theory, killbots fighting killbots could lead to very clean wars. The problem is that the least powerful party will quickly resort to 'kill and torture as many civilians as possible' as a means of revenge, psychological warfare, terrorism, etc. The ethics of robots will be the ethics of humans. More powerful and effective killing machines will amplify the behavior of immoral humans.