Come on, now. There are many better ways for screening out potential terrorists. And you would denying entry to Jews who observe dietary laws as well as vegetarians, for example.
I don't know why but you post made me think of this joke.
A priest and a rabbi were flying to a conference and decided to engage in some small talk to pass the time.
The priest asked the rabbi, "is it true you cannot eat pork rabbi?"
The rabbi nodded yes, "It is forbidden to consume pork."
"Have you always followed this law rabbi?" the priest asked.
The rabbi looked thoughtfully and said, "Once I broke down and had a ham sandwich."
The two were silent for a moment then the rabbi asked the priest, "Is it true that priests may not have sex?"
"This is true," said the priest, "we may not have sex."
Have you always obeyed this commandment?" asked the rabbi.
The priest nodded negatively, "Once I was weak and had sex."
Both men were silent for a few moments and the rabbi said, "Sure beats the hell out a ham sandwich doesn't it?"