The issue is not whether they should exist or not, the issue is this information most likely contains sensitive information relating to national security. "Some of the documents talked about how to recruit airport screeners and several of them even covered data security practices" This information could be used to "get a foot in the door" or allow someone to figure out a way around NG's data security.

Better yet, Locks only keep Honest people out! and we all know that security crackers are "honest"...