I mean...they hate the empire, but they worship an Imperial Emperor; they hate any species not Nord, but they're quick to grab any that seem to be better at fighting than them; they love Ulfric because he "stands up for true Nords," but Ulfric is trying to get rid of the Empire - which has been prevalent in Skyrim for longer than any of them have been alive (so one would think, true Nords would be loyal to the Empire - as Hadvir's father says at the beginning of the game when asked about the Empire - "Nords are no fairweather friends").
