America doesn't do drugs

Tuns out, if you're British and you've been convicted of a crime involving drugs (or anything else that implicates moral turpitude, a phrase that governs lawyers too and that I hate), you will not be permitted to enter this country without a visa. Brits can typically come to the states without one (just like we can go there without one). But they are literally turned away at the U.S. airports at which they land if they have drug convictions, or if they simply admit to having been a drug addict at one point. I get that we want to protect our country from villains and the like, but this is silly and absurd. Just because a person has done drugs, we turn them away. Murder, by the way, is not a crime involving moral turpitude, so I assume that convicted murderers in without a question. Because they're less dangerous? A British memoirist, who was arriving at Newark to attend a book party and book tour to promote his book, was deported straight away for this reason. I guess we'd rather get rid of him than read a book?