I agree with this, especially since a lot of people will interpret politeness as being a sign that your decision is negotiable.

That polite "No, because of X, Y, and Z" rapidly turns into "I have made up my mind, no" and then into "This is not a fucking debate, so no, and fuck you." very quickly, especially if you're dealing with a constant deluge of stupid requests.

I'm not going to judge Linus for his outbursts, as obviously his method seems to work pretty well.