While I don't really care and TD and Parker as classy as players can be in the NBA [especially Duncan], this will elicit some kind of fine and probably should. Guns pointed at a ref, even in jest, just isn't something the league is going to laugh about.
If it were somebody like Arenas doing this, then many would agree that action should definitely be taken. But I don't think you can take player reputations into account - no matter how positive they are.