I've emailed Derek before, asking him for some advice on improving my artwork (and my band's mascot), and he replied. He seemed pretty kind and interested in helping me out, so I don't really think he's a total asshole (or if he is, at least he doesn't blow off fan emails). He does seem bitter in these interviews though.
As for his FOTD idea that was posted above, I honestly don't think it looks horrible. It wouldn't have made a good album cover, but with a little more work, it could have been a cool shirt deisgn or something.