The terrier bandits were openly attacking the merchant from earlier, they were completely comfortable with trying to rape the protagonist when they first saw her (despite her looking like an undressed child), and they just tried to cripple what they assumed were random travelers with a throwing dagger.
Thought it likely wasn't the writer's intention, given the info on them so far, I wouldn't put a history of muggings, rape, and murder past them. With that said, it kind of rubs me the wrong way that the protagonist supports their escape, even if just for comedy relief purposes.