The world would be better without autonomous drones just as it would be better without guns or without bombs. The issue is that in a world in which the knowledge required to make a gun exists, it is in there interest of all of civilization to manufacture them and ensure that the "good guys" have enough of them and are sufficiently trained in their use to deter and exact vengeance on the "bad guys" who will develop, build, and use them regardless of their legality. This situation is identical. Knowledge cannot be destroyed (and it's very unclear of the damage caused by the destruction of the knowledge required to build autonomous drones outweighs the benefits humanity would derive from other applications of the same knowledge), so our only option as purported "good guys" is to arm ourselves. Once armed, we can attempt to construct incentive compatible mechanisms to make the use of drones of extreme negative utility, but we must be armed in case some actors have unexpected/unconventional/un-deter-able utility functions (terrorists). To propose that no smart people apply their knowledge to a particular end is idealistic and may leave us dangerously exposed.