""If you cannot read that, than you're an idiot?""
Gosh. Sorry, but that won't do either. Your sentence still makes no sense. You've corrected one error that rendered it incoherent but have introduced another common error.
"than" is a comparative word, used in constructions such as, "You're even more stupid THAN I thought."
You may have been thinking of the word "then," often used as a conjuntion meaning therefore.
If you keep trying, you'll get this simple sentence right. Then (notice the correct usage) you can work on more difficult expressions.
You are merciless. (But that one had it coming in spades.)