Your last sentence implies that everyone can be on a level playing field, which is just not the truth though. Think about rebel groups. They might use the odd drones here and there, especially with another state benefactor, but they'll inherently have to use human resources over robotic ones due to the lack of infrastructure, funding and potentially even knowledge required to produce those things. This might sound okay at first glance when we think of true terrorists like the IS and others. But what happens when the state actors become the villain and the terrorists actual freedom fighters? Especially given our current climate of rising authoritarianism within the west. Then combine AI killer swarms with AI mass surveillance and it is pretty much impossible to root out said evil again.