Marines Cover Up the killings in Haditha

Is it really difficult for me to believe that American marines would cover up or destroy evidence of their crimes (the killing of 24 Iraqis). That is really shocking! I don't know if I can digest this news since the U.S. military has been so upstanding and above board with this war. We should probably just ignore those missing files and forget the death of these Iraqis. What's 24 more dead Iraqis when we have a million ++ on our bloodied hands?