@BritTim: unfortunately this personality type isn't rare - this kind of behavior was SOP at, ah, a large semiconductor company at which I was formerly employed. It made it impossible to get anything done without an argument.
It's not a bad overall strategy - disagree with any suggestion by default and try to find good reasons why you disagree. If you can, stick to them. If you can't, then you may have to give in. Either way, you'll have a reasoned response. Blindly agreeing with others leaves you uninformed - you won't be able to argue the case either way.