More then that, player characters can't attack sleeping NPCs either. Completely overlooked this!
Been raiding the cannibal's lab the other day, and cannibals are working shifts, means, some are sleeping while other stay on guard. Those that stay on guard aggro-ing at player correctly, but some of the sleeping units lay put, and nothing can be done about it. So after dealing with active enemies, my crew stood next to sleeping cannibals, politely waiting for their wakeup
"- Sir Cannibal, would you be liking to be sliced into tiny pieces yet?
- No, Sir Walking Meat, certainly not, for i need some good rest still.
- Oh, that's fine, take your time, Sir, i'll loot your place meanwhile then.
- Of course, be my gue... zZZZzZz..."