Because he figures he's net-benefiting from the whole birther fru-fru. So, why should he stop it? "Hey, Factcheck.org said my birth certificate was legit. Normal folks believe them! You guys are just a bunch of cwazy right-wing nuts!"
Nice way to treat fellow FReeper, especially when you are woefully uninformed on the subject.
Go to the link I sent you and see what the Founding Fathers had to say about it.
Or are they cwazy right-wing nuts in your opinion too?