This is perhaps the oldest question in law and possibly civilization itself: what do we consider right and wrong, and what do we do about it?
Moral turpitude is necessarily a subjective issue, as we determine if a person actually understood that some actions are so immoral that we cannot tolerate them in our relatively moral and orderly society.
Persons who come here from Yemen or Mauritania find themselves almost immediately in violation of our laws that forbid abuse of women, abduction of hostages for ransom, contract homicide, and bribery of public officials. In their homelands these actions were part of everyday life and approved of in their holy book, the Qu'ran. Here these actions are completely unacceptable and in certain cases merit the death penalty.
Far be it from me to require denial of visa against all who come from the Middle East. Many of their people are surprisingly well behaved.
The question is, shall we compromise the moral standards that made America great, in order to accommodate persons who come from lands that are so immoral and corrupt that they cannot get along in civiization?
In short, people who come from a hellish place will behave in a hellish manner by adaptation and necessity. Can we turn these sows' ears into silk purses or should we resume the selective visa quota system that was in place from 1948-2010?