Meeting someone, even virtually, who is not only very bright and expert in their field, but passionate about it, can be exhausting. P.W. Singer is all of that and remarkably wise as well. While his most recent book is about the application of robotics to warfare, it is the third book in which he has examined who (or what) is doing the fighting, with previous works focusing on corporate warriors (mercenaries) and child soldiers.
If you haven't already, I'd recommend having a look at the video of his presentation at a recent TED conference.
As he makes clear, every image of a machine in that video depicts something either already in use or in serious development, in the hope of selling production units to the military. At least with respect to military use, the robotic genie is already out of the bottle, and the arguments in favor of deploying machines that are both lethal and autonomous will probably prove insurmountable.
Knowing what I do about robotics, and about the pressures to reduce the risks faced by American military personnel, this was probably inevitable. Robots are a shoo-in for any task which is dull, dirty, or dangerous, and it shouldn't be any great surprise if they first come into their own in applications which are frequently all three. But given the ability to build machines which can be trusted with life-and-death decisions, many things become possible.
To paraphrase Stewart Brand, we have begun to intrude on territory formerly reserved to the gods, and had damn well better get good at it sooner rather than later.