Also, while the police do deserve much of their reputation, it's worth remembering that citizens and police interact frequently, all day every day, across the country, and mostly nothing newsworthy happens.
Sure when I was 22 I felt as grown up and superior as anything, yet the same amount of years later I realise how little I in fact knew then, and still do.
Christian did the old kid a huge favour.
I also don't think Christian did the scammer a favor either. If anything Christian's interaction with the scammer may have emboldened him because even when he got caught he got away with nothing lost other than a potential reputation hit with his family. Can encouraging a known scammer to keep scamming by showing them how to not get caught and that there aren't any consequences if you do manage to get caught really be considered a favor?