It is very easy for Sarge to forget that a lot of people find him unsettling. Among the Hellhounds he doesn't stand out all that much, aside from his rank, because the whole lot of them are more or less cut from the same kind of ruffian tree. But it is usually not just his quiet demeanor and the fact that he has the ability to glare in at least fifteen different ways. The real unsettling part usually appears when he is involved in a fight.
Because he is more than ready when she swings, but he doesn't do much to soften the blow. He just looks at her and grins, taking the blow to his jaw with just the slightest of backward movements to soften it, reaching up to grab her wrist and grab her arm, twisting it around using her own momentum.
"Well, that ain't a way to make friends, let me tell ya."
Sarge doesn't feel like trying to see how much pressure he'd have to apply to her wrist to get her fingers to loosen up and take her brass knuckles. Instead he just pulls on them, leaving it up to her to decide how badly she wants her fingers to remain unbroken.