If you take the time to ask a cop why they need to see your license they might say something like, 'Because I don't know who you are' - as if identity is a product of the state and having that piece of plastic somehow gives the cop any extra insight. But try putting that the other way - insist that you need to see their license for the same reason. 'Well, officer, how do I know who you are? We've never met so, to me, you're just a stranger making threats.'