Holder claims that exposing the reason for denial of entry to the US

"could reasonably be expected to cause significant harm to national security."

Which on the face of it is true, because:

The bogus national security claims invoked were even more outrageous because they were used to continue the persecution of someone the government knew to be innocent.

Exposing the truth makes us look bad. Making us look bad puts our bullshit, freedom harming programs at risk. We serve those programs, those programs are the most important thing (and not looking bad).