I think the problem here is the wideheld concept of 'robot'. Most people hear the word 'robot' and think 'android'.
Robotic probes are already with us, some are armed. Oli linked to several UAVs.
In future we will see a wider range of remote controlled, and autonomous vehicles being deployed. Some may be armed themselves, whereas others will provide intelligence to guide weapons fired from other locations. As technology improves, it's not hard to imagine quite small scale probes, the size of insects, using a grid communication system, to call in a rail gun strike from orbit, or a round from a BFG (Big Fucking Gun) somewhere over the horizon.
Imagine that, 'is that a dragonfly buzzing around that terrorists head?' As it relays a picture back to HQ for facial recognition. Oh dear, known bad guy. 3-2-1 ZAP! Hole in the ground where the bad guy was, as the Dragonfly happily snaps more of the crowd.
Such technology will become pervasive, as it gets cheaper.
