I fully agree with AAC and Ashley. In addition, what about explaining to him that certain "wrongs" are more important than others and that maybe it would be a good idea to pick his battles? You could explain that needing a drink of water right away may be less important than watching a child be bullied, for instance. Yes, you want to allow him to define his own morals, but you can still have open discussions with him about what sort of moral compass he might want.
And you may also want to suggest that if he was ashamed of his behaviour, the best thing to do would be to admit to it and apologize. It will be a rough road ahead if he stands his ground in every battle (great or small), especially after he regrets a choice he made.
