Take military drones, for instance. People are not concerned about drones because they can be used to kill each other; we have been killing each other for millennia. What makes drones concerning is the relative ease and safety with which they allow us to kill each other. We no longer have to risk the lives of our sons and daughters to wage war in far-off lands; we can do the same from the comfort and safety of a bunker.
What does this mean? We are risking less when we wage war. Waging war is easier. This makes us much more likely to be warlike. What we previously may not have seen as a worthy cause for risking the lives of our troops may yet be seen as a worthy cause for risking our money, in the form of UAVs, robotics, ammunition, etc. On the side of the attacker, war becomes more about spending money than risking lives. That is a big difference.
Moreover, these changes have consequences for the people war is waged against as well as innocent bystanders. An occupying soldier is less likely to target and execute a civilian than a soldier piloting a drone from far away. Innocents are much easier to mistake for insurgents on a computer screen.
The psychic distance between two people is far larger when they are separated by digital rather than physical space, meaning less empathy is involved. A reduction in empathy makes it easier to risk the lives of the people you intend to ignore or protect. This is the same reason people are so mean to each other on the Internet.