I don't see why people ever worshiped every word he says as fact.
Chris Avellone, a video game designer who worked on Fallout 2, Van Buren, and more recently New Vegas, did something similar when he made the Fallout Bible. It was a massive collection of stuff that answered countless plot questions, Lore discrepancies, etc., and people treated it as fact until Chris finally said it isn't until its in the games themselves.
It doesnt matter if you were the lead lore master and wrote a massive books worth of stuff explaining all the lore errors, unless it is in the games themselves or other officially authorized materials it isnt canon.
A few responses:
1. Monkey Truth. I acknowledge that it exists. Sounds like you don't. That's okay. My understanding was that MK was extremely involved with the creation and elucidation of lore, particularly in Morrowind. Thus, any lore he contributes is far more likely to be true.
2. The boldness and knowledge with which he speaks gives him an element of authority. You speak with boldness, but I haven't seen the knowledge, yet. If you get there, perhaps I'll accept your claims as authoritative, too.
3. The community seems to acknowledge its legitimacy as canon. Why should the community not be the deciding factor, as opposed to the developer?
Oh, and I do appreciate your looking for that quote, since you quote it as fact.
EDIT: I speak in agreement with Lady Nerevar when she said, "We see it as interesting material that enriches the universe and allows for more discussion. When "official" sources give us stuff we treat it the same way."