You know, he can just say hands done:
"Look, I don't know what I doing, I am sorry, I was wrong to take somebody's work as my own. I didn't realise how serious it was, I won't do it again.
Sorry for wasting your time."
Then move on. Not enough people offer a simple apology and admit they're wrong these days...it doesn't actually take much, I mean once you recognise that we're all actually human and therefore bound to do, say and think stupid things. It's our nature. Once you do that, can anybody really criticise you for what you've done? No, because you've already done all the criticising yourself.
But then I suppose I made my own point really, I mean people are also stupid enough to not even have the sense to realise that they're human and thus instead of seeking improvement, they head in a downward spiral into becoming a complete moron. I think my friend said it yesterday, "the more I think about anthropology, the more I hate people".