It's that little display of submissiveness and vulnerability that tugs at something primal inside Derek. That Stiles is willing to bare his throat to him, trusts him with such a fragile part of himself --
He covers up the visceral, emotional reaction to Stiles's neck (his neck, for fuck's sake) with a wry smirk and shrugs a shoulder, "I think I could forsake my creepiness for a few hours, anyway."