Scarabin, on 2013-October-24, 23:39, said:
If I see someone committing a crime, don't I have a duty to act, even at the risk of spoiling his pleasure?

Oh come on, don't be silly! I was just reading this until I came across this post. There is a HUGE difference between committing a crime and behaving badly. Even in the former instance, "No", you don't have a duty to act. One might even argue that depending on the "crime", it is none of your business. For example, do you report people who are fare evaders? Do you complain to parking officers that someone has exceeded their meter time? In France, would you call a police officer because someone is wearing a burqua?