I'm an avid board gamer, card gamer, RPGer, and lover of good TV shows.
I may play a dumb paladin, but I'm not stupid. I follow the Platinum Rule: do unto others as they have done unto you.
That means: don't be insulting unless you want to be insulted back; don't assign motivations to me you have no knowledge about; and don't be an ass unless you want to be treated like the stuff that comes out of one.
That being said ... when I play a paladin in an RPG he is almost always the nicest guy ever.