President McKinley is being targeted for erasure by activists who — ignorant of his legacy or hostile to America — are calling to strip his name from a Honolulu high school.

The honor, the Hawaii’s teachers union claims in support of the campaign, “glorifies a man who illegally annexed a country against the will of her queen and people.”

For precedent, they point to a nearby middle school, just renamed for a princess who claimed to have descended from the House of Kamehameha.

If you’ve visited the islands or watched “Magnum P.I.,” you’ve heard of King Kamehameha I. His statue is one of Hawaii’s two in the Capitol’s Statuary Hall in Washington D.C.

But he wasn’t elected by islanders, either. He conquered them. Is anyone throwing his statue into the dustbin of history and replacing it with, say, one of native son President Obama?

Robert W. Merry, author of “President McKinley: Architect of the American Century,” told me, “The only reason to wish to do away with the McKinley name on anything is either through ignorance or through a feeling against America.

“Hawaii could not survive as an isolated kingdom in the 20th Century.” As one of the most strategic spots on earth, the U.K., Germany, and Spain all coveted it.

Mr. Merry calls Hawaii an “obsession” for the Japanese Empire, who flooded it with colonists as Russia did Crimea before seizing it.

Imagine Japan or Nazi Germany entrenched at Pearl Harbor in World War II. With territorial status, McKinley prevented that nightmare.

“We were not a bad nation because we acquired Hawaii,” Mr. Merry said, “and we didn’t acquire Hawaii because we were a bad nation. It was the natural course of events.”

Ben Justesen, author of “Forgotten Legacy: William McKinley, George Henry White, and the Struggle for Black Equality,” agreed.

The renaming campaign makes it seem as if McKinley, he said, “was somehow responsible for all the events before his presidency that he certainly couldn’t control.”

The overthrow of an unelected monarch, declaration of a republic, and so-called presidency of Sanford Dole all predated McKinley’s election.

“I think there are less historically thoughtless ways to handle it,” Mr. Justesen said, “without tarnishing his legacy completely.”

It’s this legacy that earned the school its name in 1907, six years after the president was gunned down; it wasn’t intended as a fork in the eye of natives.

As historian Annette Gordon-Reed told the Harvard Gazette of similar campaigns, “No one puts a monument up to Washington or Jefferson to promote slavery.”

She added “The monuments go up because, without Washington, there likely would not have been an American nation,” and without McKinley, there would not be a 50th state — or a Union for it to join.

A staunch abolitionist, McKinley enlisted in the Civil War at 18 and served all four years, including at Antietam, the bloodiest day in our history. 

“I weep for the poor people of Hawaii,” Mr. Merry said, “who wish to insult the memory of a good man such as William McKinley — or the memory of America at the turn of the last century — either through ignorance or a lack of regard for their own nation.”

In 1897, a column in the Sun bestowed the name McKinley on the highest peak in North America because the writer thought he had earned the honor.

President Obama restored one of the many Alaskan native designations — Denali, meaning only “the tall one” — in 2015, despite objections. 

At the time, Mr. Merry and I agreed that whatever we might think, the 25th president was humble, and would have shrugged at losing the honor.

McKinley might not mind the school being renamed either, or even the lies being told about his life and the modern press omitting mention of accomplishments or, for that matter, his assassination.

McKinley, though, is more than a man now. He is a martyred president and a symbol of American greatness. As such, he deserves a defense before his name is swept into a dustbin where it doesn’t belong.