First, a little backstory. My son Mac is only nine years old, but possessing a vivid imagination fueled a lot by his father’s flights of fancy. His exposure to D&D in almost entirely informed by The Order of the Stick, the Dragonlance movie, and kid-friendly MMORPG’s like Dragonfable or Adventure Quest. He’s also been reading through the 3.5 and 4.0 editions of the PHB.
He’s interested in paladins, which means he’s interested in the gods of D&D. OotS has Thor and the Twelve Gods of Azure City. Dragonlance has their own gods. The PHB has others still. The whole notion is confusing to him. In addition, I get questions like:
Which races like to fight a lot? Do elves like to fight? What about dragonborn?
Do half-elves like to fight if they are overcome by their human half? (A Dragonlance reference)
Do all paladins wear capes? What about other classes?
Is Riverwind a barbarian? Etc…
Finally I just had to silence his questions and tell him the following:
You keep asking me what D&D says about gods or races or whatever. There’s no set answer to these questions. It’s about your story. You want elves to like to fight, then they like to fight. Anyone can wear a cape because you decide what your character is like. Gary Burlew made up all the stuff in Order of the Stick. Margaret Weis and Tracy Hickman came up with the gods and the dragonlances and even the kenders in Dragonlance. When Pathfinder finally shows up you and I can make up our own story with whatever gods and races and whatever we want, because that’ll be our story. The answers to these questions aren’t in the rulebooks, they are in your head.
You got to get this stuff embedded in now, while they’ll still listen to you.
Strange Vistas 
He likes rules and things “set.”
I can understand, to some extent, though. Think of all the people who want their army background to fit the fluff, and freak out if they don’t know what symbol they should be painting on shoulder pads for rank and what not.
I got into role-playing a couple of years before I got into miniatures gaming (Battletech, specifically, then 2nd Ed. 40k), and one of my initial reactions to miniatures gaming was a sense of disappointment that things had already been decided for the player–the stats of your figures, the color schemes for the army, etc. I howled and resisted, coming up with alternatives (my own space marine company, Battletech mercenaries using Mechwarrior characters as pilots, etc.). And this was back in 2nd edition when there was still a certain level of customization, before 3rd ed. smoothed a lot of things over.
Needless to say, it took a long time for me to get used to that notion, that customization or ‘character’ in a miniatures game (historic or non historic) meant color scheme, how you interpreted the ‘fluff’, and army composition, as opposed to having every member of every unit a well-defined individual.
(by the way, I can understand this attitude a little better in historical gaming, especially if you’re trying to recreate specific battles between actual forces; but then, I was never interested in such things 🙂 ).
When D&D 3.5 came out and I started playing with a group of ‘character optimizers’, I found myself confused again, as the rules for miniatures gaming army selection suddenly appeared in my role-playing games. I never considered the idea of ‘optimizing’ my character or being told (as 4th ed. does) that such-and-such a race are good [this class] and are bad at [that class].
Now I _may_ be finding myself in a GURPS Weird War II/Delta Green-Call of Cthullu-esque game (really fast and dirty description) and I’m forcing myself to go back to where I was, gaming-wise, in my youth, when I just wanted to play cool character concepts or ideas (not necessarily based on their stats) and see where the character went…I’m finding it takes a lot of energy and time to unlearn what has been learned…