Can someone explain to me why it would harm our national security for Gitmo prisoners to be given due process?

It's pretty simple. If the bad guy was a bad guy, it'd be proven. If he didn't do anything wrong, just someone in the wrong place and time, it'd be proven and it would make no sense morally or financially to hold him anymore. Can someone give me a good reason why we should keep Achmed the pizza delivery driver who stumbled into the wrong neighborhood or something? Obviously cons will say that everyone in Gitmo has done something to deserve being in there, but how can they be sure? Even if 500 people witness an American committing a crime, he still gets the benefit of doubt and a trial, but why ought not this principle apply to those in Gitmo? Just in the off chance that Achmed knows where a big weapon stash is, or is simply looking suspicious enough of a reason to put somebody in an orange jumpsuit, torture them and lock them in tiny cells? Or maybe the reasoning is that we already tormented him so much that if we let him go now he'll just go join some terrorist group to get revenge. If that's the case why don't we just start executing them?