It's not every day that the U.S. Department of Homeland Security revokes a visa issued to a Swiss-national scholar scheduled to teach at one of America's premier universities. But this has just happened, and it's a good thing too. The Swiss scholar is Tariq Ramadan. He is Islamist royalty – his maternal grandfather, Hasan al-Banna, founded the Muslim Brotherhood, probably the single most powerful Islamist institution of the twentieth century, in Egypt in 1928. Tariq is a Swiss citizen because his father, Sa‘id Ramadan, also a leading Islamist, fled from Egypt in 1954 following a crackdown on the brotherhood. Sa‘id...