Why so secret?

Last year a U.S. plane bombed the Doctors Without Borders hospital in Kunduz, Afghanistan, killing 42 patients and health workers and injuring many more. The Pentagon has investigated the affair and says it was a mistake, not a war crime. But there is no way to verify the Pentagon's conclusion as almost all of its report is redacted for the peasants, but available to those with a top security clearance. Should we be satisfied with this conclusion that the affair was “a combination of human errors, compounded by process and equipment failures”? 

Interestingly, the 4th Geneva Convention, Article 18, states unambiguously that “civilian hospitals organized to give care to the wounded and sick, the infirm and maternity cases, may in no circumstances be the object of attack, but shall at all times be respected and protected by the Parties to the conflict.”