This is actually something I've thought a good bit about. As robots become more militaristic, an armed populace becomes less of a threat to their government. There's a good sci-fi story in there somewhere.
I disagree. I think robots will actually decentralize power. The key to all of this is software which, as we’ve seen, is effectively impossible to lock up. So I think what you’ll see is the proliferation of cheap, effective drones armed with explosives that are extremely difficult to defend against.
We’re seeing this play out in the Middle East, most recently with a drone attack on Saudi Arabia’s oil production.
I definitely support civilian ownership of self-defense robots. But for them to be affordable (or maybe even possible), there needs to be substantial production of non-defense humanoid robots like robot maids to build up the supply chain. Even then humanoid robots have a lot more moving parts so they'll never be as cheap as today's civilian drones.