Your answer is in your question - disclosure of criminal acts certainly is an exception. If the acts involved were immoral, but not criminal, then you'd have a

Your answer is in your question - disclosure of criminal acts certainly is an exception. If the acts involved were immoral, but not criminal, then you'd have a quandary, but in this case, you may even find that not reporting their actions (depending on what they are/were) could come back to bite you.