John is entirely innocent of any involvement in the terror attacks, or any allegiance to terrorism. That is not disputed by the American government. Indeed, all accusations of terrorism against John were dropped by the government in a plea bargain, which in turn was approved by the US district court in which the case was brought.
Paternal concern is indeed honourable.
But seriously, using the “we’ve no evidence” part of a plea bargain just doesn’t prove that there’s no evidence.
As you go on to point out, your son was a trained and armed soldier in the service of the Taliban.