The Army’s goal is to train Soldiers to do the right thing even when it’s painful. Your unwillingness to provide information on what you saw is unfortunate. You may see it as ratting or being a snitch, but the Army sees it as maintaining good order and discipline.
Perhaps we should look at this a little differently. You are at the local convenience store and someone sneaks up behind you, beats you up, and takes your wallet. He walks over to his buddy and asks him, “Did you see me knock the crap out of that kid and take his wallet, Gus?” “I sure did, John.” Ten minutes later, the police show up ask you for your side of the story. You report that Gus saw the whole thing and he even knows who your attacker is. When the police walk over to question Gus he shrugs his shoulders and refuses to bear witness.