Can you use hacked drones to attack other enemies?

According to this thread in the Klei forums, yes, it is possible to use hacked drones to attack other enemies, as long as the drone has weapons installed:

Using them only for attacking is missing their potential.

And I never said hack them and attack. I just noted IF you use them to attack, they are a one shot weapon.

I've got out of a few sticky situations by hacking a nearby Obake drone and getting them to kill a guard threatening one of my agents.

This has all of the usual disadvantages of killing guards, of course. Drones also have limited ammunition, so hacking an Okabe for a third time I found it out of ammo. Also, Obakes can kill each other, so in one game I used one Obake to kill another after it had run out of ammo, clearing the way for my other agents to get past it.

I find it is generally best to avoid killing or even knocking out guards, due to the escalation that causes, but sometimes it's the only way.