He sets them on fire before they get close.

"A human keep a darkspawn as a... a... No. No, no one's that..." Except there are people who are that stupid. Most of them wear Templar armor. "Okay, so I could see a Templar doing that, but most aren't that dumb. Most also don't go deep enough to find Darkspawn; it's generally when they're pouring out of the underground, yes, that the general populace tends to see them. By that time it's in numbers enough to wipe out the whole village. We go down and take out the small pockets before they've a chance to do that."