Stupid is as stupid does; or, Objective is subjective - I

What exactly is stupidity? Is it the tendency to act in a way that betrays a lack of good sense / judgment? But if that's the case, then isn't it all entirely subjective? After all, the person whom we think is acting stupidly is doing whatever he is doing because, to him, his judgment is pretty sound, just as we think our judgment is sound.

Expanding on this theme, is there anything that we could talk about in absolute terms? Even God? I'm afraid there isn't, because for each thing we think is absolute, there's a likelihood that to somebody else, it's not so; it's also likely that to that person, there's something else that's an absolute. At the risk of oversimplifying it, I'd like to state that reality, truly, is purely subjective; objective reality just does not exist. We create the reality we live in, otherwise why would Osama bin Laden have supporters? Sometimes, though, we choose to alter our view of reality (or are made to shift our viewpoint), and thereby experience "paradigm shifts".