I never said I’m a snitch, and I definitely don’t encourage people to snitch. My point was that we shouldn’t even have anything to snitch about. We have a mitzvah to follow the laws. If we do something wrong and someone snitches, it’s not his fault – it’s the fault of the people who broke the law.
As for the halachah of a moser, there was a psak given recently after the events of Deal occurred. I believe it was R’ Moshe Shternbuch, althogh I’m not 100% sure. Basically, he said that there is an obligation of dina d’malchusa in the US, and if someone breaks the law here, they are transgressing the mitzvah. In such a case, there is no din of mesirah on it. Mesirah applies when someone did nothing halachically wrong.
I’ve been told that in countries where they make laws specifically targeting Jews, there is no dina d’malchusa. So, when there were taxes levied on Jews and nobody else, snitching on someone was mesirah. Snitching on a criminal in the US is not mesirah.