"Drones" is a broad term, encompassing both the friendly multirotor type that carry GoPros over snowboarders, and the more menacing UAV type that fires rockets into convoys. The safe kind requires little more than a credit card to acquire, whereas the dangerous kind needs an encrypted satellite uplink and a team of burnt-out pilots manning workstations in Nevada.
Those differing barriers of entry are why I don't like the idea of weaponizing the former. Yet it's happening, though the people doing it may not realize they're doing it. First graffiti artist Katsu rigged up a drone that could spraypaint. If multirotor drones can spray paint, then they can spray other compressed gasses, which I imagine has to give a terrorist ideas. And now a power company in China has rigged up a drone that can spray fire.
What's happening is that airborne garbage is getting caught on overhead high voltage lines. The company reckons that the most efficient way to get it off is to burn it off--I guess this is what happens when you don't have an OSHA or an EPA--and a multirotor is easier to send up than a worker in a hydraulic bucket.
All I can think about is how much damage something like this could do in, say, Manhattan. A firefighter's bane is a blaze he cannot easily get to, and what we see here seems like the ideal way to start hard-to-reach fires.