You can't simply stop warfare by telling people not to work on munitions - World War II illustrates this perfectly. If you doubt it, consider this: some of the scientists working on the Manhattan Project considered the possibility that an uncontrolled nuclear explosion in the open might contaminate the Earth's atmosphere and eradicate all life on Earth. Despite this possibility, they went ahead and tested it anyway, and hang the consequences. If these "boffins" were prepared to risk the destruction of all life on Earth in their pursuit of more effective weaponry, what makes anyone think that the prospect of a mere dystopian horror future is any kind of discouragement?
However, things balance out. People like the Rosenbergs, who were executed as traitors for providing atomic bomb secrets to the Soviets, actually did humanity a great service by ensuring that others besides the trigger-happy USA had the Bomb, and thus vastly reduced the possibility of nuclear war through the principle of Mutually Assured Destruction. If the Americans had remained the only ones with nuclear weapons, with no other country having any effective countermeasures, I'd bet 10 years' pay Hiroshima and Nagasaki would have only been the first of many nuclear targets; Korea, Vietnam and the Middle East would in all likelihood be glowing glass wastelands by now if the USA believed it could deploy nuclear weapons without fear of like retaliation.
With robotic weaponry, a balance will also be struck. Countermeasures will be devised the moment these things start to become a problem for anyone with the ability to develop such countermeasures. Iran has already shown us that this is possible, with the drone they downed and captured and which the USA so ardently denied was anything consequential.
Those with a need to protect themselves against such devices will certainly do so, and the solutions will invariably be much simpler than the robotic systems themselves. I picture radio jamming devices, which cut off the drones from their controllers; laser pointers to blind or damage the cameras mounted on them; microwave beam emitters to fry the circuitry controlling them (didn't a bunch of boffins just recently demonstrate a powerful room-temperature maser? That has some potential...!)
Remember, it is easier to destroy than to create; a principle which in this case works against the complicated systems of robotic ordnance.
I am reminded of Arthur C. Clarke's solution to orbiting weapons satellites; he said the best way to get rid of them would be to simply launch a rocket with a payload of ordinary sand, to be dumped into the path of the satellites. The high relative velocities of satellite and sand grains means that as soon as the satellite hits the sand it would be shredded like a tomato in a sandblaster.
And I am reminded of a Commodore 64 cracking crew I was in contact with back in the 80s; a well-known game house had spent thousands of dollars and more than six months developing a DRM system to prevent copying of their games; this cracking crew broke it in less than 10 minutes for no cost. That's months of work and thousands of dollars rendered useless in minutes!
So I'm certain that the more these robotic weapons are developed, the quicker people will develop countermeasures. And those countermeasures will be something cheaper and more readily available than the robots they are intended to fuck over. Instead of pleading with engineers not to work on robotic weapons, which is an exercise in futility, get other engineers to develop ways of counteracting them. I'll be interested to see what creative anti-robot measures people come up with.
For what man can make, man can break.