Emerging technologies like robotics for war and peace stress our moral norms and generate much public interest and controversy. We use this interest to attract participants to an innovative on-line survey platform, designed for experimenting with public engagement in the ethics of technology. In particular, the N-Reasons platform addresses several issues in democratic ethics: the cost of public participation, the methodological issue of feasible reflective ethical equilibrium (how can individuals in a large group, take into account the ethical views of (...) all others?), and the reliability of public participation processes. We sketch the motivation and design of the N-Reasons platform, stressing the need for a practical (fast, low-cost) instrument that makes equilibrium feasible. We focus on the Robot Ethics Survey that featured a set of nine ethical challenges raised by robotics for war and peace. Over 400 people in five disjoint groups participated in this on-line survey experiment. We analyze the results, both quantitatively and qualitatively, the participants’ decisions taken and the reasons supporting these decisions. Both decisions and reasons strongly distinguished lethal military robotics from peace-related robotics. Methodologically, both decisions and reasons over five distinct groups were remarkably consistent. (shrink)