Here’s the thing about principle.

Unless applied equally it is not really principle at all. He who climbs on his moral high horse when a wrong is done to him or his, but leaves the horse stabled when an identical wrong is done to someone else, acts from self-interest and that is the opposite of principle.

All of which renders rather hollow the GOP’s recent chastisement of its problem child, Donald Trump, over an insult to Sen. John McCain. As you’ve no doubt heard, Trump, speaking at a conference of Christian conservatives, took issue with a suggestion that McCain, a Vietnam-era Navy flier shot down by the North Vietnamese, is a war hero.

“He’s not a war hero,” Trump shot back. Then, perhaps hearing what he had just blurted, Trump turned smarmy and facetious. “He’s a war hero because he was captured,” he said, in the same tone you might use to say someone is a poet because he scribbled a limerick on a bathroom wall. “I like people that weren’t captured, OK? I hate to tell you. He’s a war hero because he was captured, OK? And I believe — perhaps he’s a war hero.”

McCain, should it need saying, is a war hero, period, full stop. If that term doesn’t fit a man who survived five brutal years in enemy hands — and refused an offer of release as the son of an American admiral because it did not include his fellow captives — then it doesn’t fit anyone.

So Trump deserves every bit of scorn his party has heaped upon him. He deserved to have Jeb Bush call his remark “slanderous” and Rick Perry to call it “offensive.” He deserved Rick Santorum’s tweet that “McCain is an American hero,” and the Republican National Committee’s statement that “there is no place in our party or our country” for such remarks. In a word, he deserved condemnation.

But the people who slandered John Kerry deserved it, too. The secretary of state is also a war hero, period, full stop. If that term doesn’t fit a wounded man who braved enemy fire to fish another man out of a river, then it doesn’t fit anyone. Yet in 2004 when then-Sen. Kerry ran for president and a shadowy Republican-allied group mocked that heroism and baselessly called Kerry a liar, the GOP had a different response.

Jeb Bush wrote a letter praising those who questioned Kerry’s heroism. Perry declined to condemn them. “I think that there’s a lot of questions,” he said. Santorum said Kerry “brought this upon himself” by emphasizing his military service. And Republicans went to their convention sporting small purple bandages in mockery of Kerry’s Purple Heart.

That behavior was what Trump’s comment is: shameful. It is to their discredit that so many Republicans failed to condemn it as such. Interestingly enough, at least one did. His name was John McCain.

Perhaps he understood that principle is not politics. And that what is right does not change from red state to blue.

This much is surely right: It is a sin to mock the honorable service of those who have gone into harm’s way on their country’s behalf, particularly if, like Trump, you’ve never served a day in your life. We’ve seen a lot of this in recent years: It happened to former Democratic Sen. Max Cleland, who left three limbs in Vietnam, happened to the late Democratic Rep. John Murtha who spent 37 years in the Marines, happened to Kerry and has happened more than once to McCain.

Principle — a decent respect for the sacrifices of military men and women for this country — demands that patriotic Americans condemn this, no matter who it happens to. But if, somehow, your condemnation depends on whether the insulted person is of your political party, please understand that there is a word for what motivates you, and “principle” is not it.

“Hypocrisy” is.

Leonard Pitts Jr. is a columnist for the Miami Herald. Readers may write to him via email at: lpitts@miamiherald.com.