It's not his job to "prove" his lack of guilt....only Fasicst thing someone has to prove their lack of guiltThey did not just "hurl some accusation."
You use a false equivalency here.
They accused him of taking top secret material he should not have had.
And when they executed a search warrant to look for that material they found it.
Of course he was unable to "prove" his lack of guilt because the EVIDENCE found clearly proved otherwise.