The reason for it currently to be "for non-offensive uses only" is NOT because making the machine to automatically kill someone is unethical, but because it's is not accurate enough to only hit valid targets (May hit deployer and friendly).
So yeah, may be now it's "for non-offensive uses only".
Few years in, it will be "human control the kill trigger".
Then, eventually, it will be "human deploy the device, then it fires and kills all by itself, just like a fire-and-forget missile, plus it can hit multiple targets and be reused."
The dark side of technical advancement.