Truthers aren't actually concerned with evidence or facts. I was arguing with one on Youtube who claimed Muslims don't have sea burials. I provided evidence they did, and he said he didn't need to click the link because he knew already. He knew something he had said was false. This didn't trouble him one bit.
If Osama had been found early in the War in Afghanistan, it would've been suspicious to them. Since he's found over nine years later, it clearly means the gov't killed him years ago and had the body hidden, and buried him at sea to keep The People from giving him an autopsy on US soil. If they had bought him to the States and given him an autopsy, Truthers would claim that the gov't was parading him around to distract The People from the Truth, and that the people giving the autopsy were compromised.
They'll just keep moving goalposts, the logical equivalent of a Jedi Mind Trick, and there are plenty of weak-minded.