There's a perfectly good explanation for why US Customs refused Ian MacEwan entry to the country. It wasn't because he was dangerous; nor was it because he was deemed to pose some kind of terror threat. Nor was it because someone thought he might be a journalist instead of a tourist. It apparently wasn't even because he disagrees with US climate policy and doesn't mind saying so in public.
It was because he was going to make too much money. It seems the honoraria for his series of Seattle-area speaking ingagements totaled a wee bit too much. So he needed to have a work visa, not a tourist visa.
So they stamped his passport "Refused Entry." "Once that stamp gets in a passport, it's difficult to get it out," said Britain's Consul General for Vancouver, James Rawlinson. "The process of reversing that is not merely a matter of crossing that out. Reversing that requires referrals to Washington, D.C., and the headquarters of the State Department and Homeland Security. It gets rather heavy."