Autonomous cars will for sure be more efficient on safety and decision making. What I think they are warning against is the potential efficiency of AI machines

Autonomous cars will for sure be more efficient on safety and decision making. What I think they are warning against is the potential efficiency of AI machines at war. Wars could happen in minutes instead of years. You mention more legitimate targets being killed and fewer innocents, but how are those being defined? There has been multiple points in history where the set of 'legitimate targets' by a group was defined by everyone not in their group.