>People might use it for killer drones after all.

For some reason drones are perceived to be completely different from all weapons that have existed before them. Those killer drones have existed for half a century. They are called missiles. Also the reason why UAV based fighter jets are not viable is because a cruise missile can be launched from 1000 miles away and for the cost of a global hawk you can send out more than a hundred of them.

If terrorists have access to explosives then it doesn't matter how they deliver them because most lucrative targets (= lots of people in a small area) are stationary or predictable. A simple bagpack filled with explosives was more than enough to injure hundreds of people during the Boston Marathon.