Looking at the 'defensive lines to take' in the original post, reminds me of the classic Yes Minister series.
Any time they wanted to trash a report certain lines were taken. Some of the statements in the quote above look very familiar.....
Remember the Official Secrets Act is not to protect secrets: it protects officials.
According to Sir Humphrey, try one or other of the following:
It leaves important questions unanswered;
Much of the evidence is inconclusive;
Certain findings are contradictory;
Some of the main findings have been questioned (if not, question them yourself)
Thinking back to air shows (remember those?). Every time a 'low observable' aircraft flew past it would have a couple of F15's in close escort. Maybe the same applied in the case above.