Or because people will use them to remove military security?

Exactly. Unless some kind of corresponding defense evolves, they're going to democratize sanitary application of force, which has largely been a privilege of governments until now. (Sanitary to the people ordering it, not to the people directly involved, obviously.) Can you imagine what ethnic cleansing would have looked like in the Balkans if the Serbs had been able to afford thousands of predator-style drones? It won't be long before the cost comes down to the point where they could have.

Not really, some of the tech on the predator is not cheap.

The easy part is making the plane, I'm sure you could rig up a cessna like Hollywood rigs up stunt cars for remote control and you'd have a "UAV" (didn't Iran do that already?).

The guided missiles, the communications, the optics and sensors, those are the hard parts.

I honestly think a bunch of boots on the ground with rifles is the scariest way to do ethnic cleansing, if you just want to level houses you have artillery and tanks too. The predator is good for surgical strikes and intelligence, which a lot of enemies really don't care about.