Once upon a time, “moral relativism” — the tendency to draw comparisons between the conduct of the United States and its enemies — was the bane of American conservatives.

In his famous 1983 speech to the National Association of Evangelicals, President Reagan said, “I urge you to beware the temptation of ... blithely declaring yourselves above it all and label both sides equally at fault, to ignore the facts of history and the aggressive impulses of an evil empire.” Reagan’s ambassador to the United Nations, Jeane Kirkpatrick, wrote, “There is no more misleading concept abroad today than this concept of … superpower equivalence.” In 2011, Rep. Paul Ryan, not yet speaker of the House, said, “If you ask me what the biggest problem in America is, I’m not going to tell you debt, deficits, statistics, economics — I’ll tell you it’s moral relativism.”

And throughout the Obama administration, conservatives excoriated the president for supposedly apologizing for past American actions such as the nuclear bombing of Japan — and for not doing enough to champion the doctrine of “American exceptionalism,” which holds that the U.S. is different from, and implicitly better than, ordinary nations. In 2015, for example, then-Gov. Bobby Jindal of Louisiana complained: “This is … maybe the first president ever who truly doesn’t believe in ... America as a force for good.”

So it is more than a little ironic that the chief font of moral equivalence today is a Republican president who has the support of many conservatives — including Ryan and Jindal. President Trump has no problem trashing allies such as Australia and Mexico or bad-mouthing NATO and the European Union. But he will never say a bad word about Russian dictator Vladimir Putin.

The latest manifestation of Trump’s disturbing bromance with Putin came in his Super Bowl Sunday interview, in which he once again touted the virtues of “getting along with Russia.” Bill O’Reilly challenged him: “He’s a killer, though. Putin’s a killer.” Trump was nonplussed: “There are a lot of killers. We’ve got a lot of killers. What, you think our country’s so innocent?” This is no slip of the tongue — it is a repeat, virtually word for word, of comments that Trump made in December 2015 on Morning Joe. When Joe Scarborough said Putin "kills journalists,” Trump insouciantly replied, “Well, I think that our country does plenty of killing, too, Joe.” ...