If the ignorance of the general public, or even minorities in it, got to us at every moment we would certainly live rather miserable lives.
Just let him be in his delusions, he is well within his right to continue to be wrong. It is not my, nor anyone else's, problem that he doesn't want to learn. There is only so many ways one can repeat logical arguments before it is depressing.
When AzN understands how a GPU is manufactured, what scaling means, and how crossfire works (your repeated refusal to even basically understand that crossfire is not a straight doubling is beyond me.. yet you still use the 4870x2 as proof...) then we can have a discussion. As it stands we may as well go argue with creationists about evolution. They are just as stubborn in their refusal to accept reality.. but at least it is hilarious.
"I'm right because your wrong, anything you say is wrong because you are wrong, so I've proven that I am right." Seems to be the way this sort of thing works with fundies.. not much different here.
By the way, there is nothing wrong with extrapolating performance based on specs. But you are extrapolating reasons for this performance based on specs that you are misunderstanding, and you choose to ignore aspects of the specs that make you seem even slightly less right. That is the issue, there is obviously nothing wrong with honest theoretical discourse.. It is perfectly scientific if done correctly.