Agreed. The really interesting point of the "How NOT to build a Terminator" talk was not just that we had to avoid building evil machines, but that we have the potential to build machines with better ethics than human soldiers. Avoid atrocities committed to angry soldiers, avoid accidental wars started by twitchy trigger fingers, avoid intentional wars started by people who weren't authorized to start those wars, that kind of thing. The devil is always in the details, but a ban can only ensure that the people building these weapons are the ones that won't put in the proper effort to make them good.