Everybody must respect the Law. This doesn’t mean that mosques must be banned from Italy or that we cannot learn from other cultures.
The majority of people who believe in the premises of this theory see every African as a potential rapist, every Muslim as a potential terrorist (or, at best, one who beats women), and Romani, Romanian and Albanian as a thief. This vision clearly lacks of realism, depth and objectivity.
There is a serious debate among Law doctors about how to deal with actions that are considered crimes only by one culture. The debate is still open, and the people involved are too impartial to be considered supporters of a specific politic philosophy.