You are wrong. I know a pure keyboarder that had to stop after an hour because of headache and burning eyes. True, he was unable to identify the issue exactly, and though it was generally improved brightness or something like it. The difference is that clickers immediately notice what is wrong, while others take a little longer.
Also, lose the arrogance. The only thing clickers are worse at is high-speed PvP. For everything else there is no difference. We have tested this in WoW using damage meters, combat log, etc.. What was noticeable though is that keyboarders _think_ they are better, but the facts say different. The only exception we found was the Rogue, because positioning is very critical for that class. What is also true is that _keyboarders_ will get worse when restricted to clicking. This is of course for experienced players only. Newbies will always be clickers, but them being worse players has nothing to do with that. For experienced players, it is a matter of taste and possibly ergonomics. And no, clicking does not necessarily have worse ergonomics, it depends a lot on the individual player.