Chikane's Law
From this wank:

If your response to a carefully reasoned, logical, and well-thought-out argument is to tell people to go back and reread what you wrote, you lose at life, the internets, and everything.

Edited to add this corollary, suggested by eljuno:

"If, on the other hand, the answer is obviously because someone HASN'T read what you said, this law is null and void. To cover, say, the day when I found myself having to ward off people who were trying to explain to me why Michael Corner wasn't (necessarily) black and all I could do was go 'I AGREE. LOOK BACK AT WHAT I SAID.'"