It remains debatable whether Sharia (the political/legal system) CAN be separated from Islam (the religious faith) --- many say they can't ---but what makes this "religious faith" uniquely offensive is that Islam IS attached to Sharia.
And Sharia is not just a public ethical aspiration, on the level of "thy Kingdom come, the will be done, one earth as it is in heaven." THAT (a phrase from Christianity's most central prayer, the "Lord's Prayer" or "Our Father") is a pledge of a believer's moral behavior, not a political program.
But Sharia has 1400 years of formal jurisprudence behind it. It has been a program of political domination and conquest from Day One, and remains so. It is a legal code built for propagation by force.
People have to understand this. I think Gingrich gets it.
Newt is correct to ask muslims if they believe in Sharia. They would never admit it and it wouldn’t work in reality, but it lets the country and its citizens know where it stands against radical Islam.