Politeness works fine with many people in many circustances, and it has bought me out of a few pinches. I've seen a cop's face go from suspicious anger to placidity from a smooth handling of their concerns. I'd wager that most of the time, politeness won't hurt and sometimes it will help. Sometimes though you're right, particularly with law enforcement, if someone is in a bad mood and on a power trip it will not make one iota of difference. What I took from this is to pay attention, there's no need to consistently clam up like this guy does, but remember it's an option because sometimes it may be necessary.