Tom T, I disagree. TJR is right on this. The lesson being taught isn't that he shouldn't be selfish. The lesson being taught is that when someone (in this case, josey) wants something, and the person possessing it indicates they are not OK with it being taken, then it's still OK to reach in and take it anyway.
Let's face it: If the shoe was on the other foot--That is, if josey's son wanted something off of josey's plate, asked permission to take it, josey had said "no", and his son had taken it anyway, he likely would have been punished. But these exact same actions are what josey, his role model, did.
josey, you did say that "he always takes my gatorades, pizza bites my chapstick or whatever it is I have, and I have no problem"--but that is a different situation, because you did not indicate disapproval when he asked if he could take them. (I'm presuming he asked permission to take those items in those situations. If he didn't, then that is an issue that should have been dealt with at that time as well. Simply put, he needs to learn that it's unacceptable for either him or his father to take things without both asking and being given permission first.)
Sorry, but if you intentionally give the child the ability to set a boundary (as you did when you asked if you could have a bite), and then you violate that boundary, I can't blame him for being upset about it. (I will agree with everyone that his response was inappropriate and needed to be dealt with accordingly, but that's a separate issue.)
He won't learn to respect others' boundaries if his role model doesn't respect others' boundaries.