Yep. Newbie rant.
I will mop the road with you, me on my MTB and you on Contador's bike. But my rando bike and MTB both have the same riding position, but the MTB still looses about 2-3mph on the road and will loose in any sprint. That is a real but comparatively small difference.
If I want to win a race against 30 other guys that are within 1% of my fitness, I will take every .01% advantage I can get! I don't think anyone is saying the bike makes no difference, just that the riders strength is by far the biggest factor. You can't make a thoroughbread out of a donkey by buying him a fancy bike (EPO maybe). Don't waste your money on fancy bikes if the old lady on a trike is going to smoke you anyway.
Why is my MTB slower? Knobby tires, wide Q-factor, suspension fork, wider arm position. But it is still a lot of fun to ride, any time, any where!