I like how he's all like "You wanna take ME on?! Forget this, I'm gonna go get me another pair of arms." And wanders off like he should be wearing a leather jacket.

Allow me to translate. After flicking your body into the wall like a wet doodle, he says "You think that's air you're breathing? huh..."

I think the Dreg simply stepped backwards just as you tried to knife him. By moving just barely out of the way, you knife the wall instead and it causes you to get flung against the wall very hard.

I had a Dreg sidestep my attack the other day and knife me immediately in the back. They can be tricksy. It's a good thing they don't do much damage by themselves.