After smashing through the gates of the Naval Reserve Center in Chattanooga in his rented Ford Mustang convertible, Muhammad Abdulazeez, 24, murdered four Marines and a sailor with his AR-15 semi-automatic rifle.

Minutes earlier, Abdulazeez had wounded a Marine during a drive-by shooting of an Armed Forces Recruiting Center. He was killed in a gun battle with Chattanooga police, but not before wounding another Marine and a police officer.

The death toll would have been higher had not Gunnery Sgt. Thomas Sullivan and Staff Sgt. David Wyatt sacrificed themselves to permit other Marines to escape, the FBI said.

“Our Marines acted the way you’d expect,” said Maj. Gen. Paul Brier, commander of the 4th Marine Division. “Some willingly ran back into the fight.”

In a related story, flamboyant businessman Donald Trump had a substantial lead for the Republican nomination for president in polls last week. It wasn’t until five days after the massacre that President Barack Obama ordered flags at federal installations be flown at half staff in honor of the Chattanooga victims.

The day before, Donald Trump had ordered the flags on all his U.S. properties flown at half staff. This well-publicized action likely shamed the president into acting.

“This disgraceful omission is unacceptable and yet another example of our incompetent politicians,” Mr. Trump said. “It is a simple yet meaningful and important gesture that signifies our respect and recognition for these great soldiers who lost their lives.”

“I like it that he’s not a politician,” Trump supporter Paula Johnson told CNN’s Alisyn Camerota Wednesday. “I’m tired of politicians. I’m tired of the sugar coating that they tell us.”

The Donald is popular because he says what he thinks, and he has all the right enemies, wrote Weekly Standard Editor Fred Barnes.

“People are looking for any candidate who can't be bought off,” wrote Carol Roth for CNBC. “Many Americans are also done with political correctness. Mr. Trump, despite the language in which he often communicates, gets points for not being worried about offending anyone.”

Many in the news media despise Donald Trump because “he has no fear, he could not care less about censoring himself, and the press does not intimidate him,” said Fox News talk show host Bill O’Reilly. “The media believe that they must punish Mr. Trump … for not cowering before them.”

His attacks on the news media get the most applause, noted Matt Welch of Reason magazine.

The Trump boomlet is causing angst amongst establishment Republicans, who fear his sometimes erroneous, often exaggerated, usually crude remarks harm the GOP, and among conservatives, who note that Mr. Trump isn’t one of them.

“He’s been pro-abortion, pro-gun control, pro-tax hikes, pro-single-payer and is a past master of crony capitalism, to say nothing of his political and financial support for the Clintons and Barack Obama,” said GOP political consultant Rick Wilson.

Mr. Trump is “a cancer on conservatism” who “offers a toxic mix of demagoguery, mean-spiritedness and nonsense,” and Mr. Trump reminds him of the late Sen. Joseph McCarthy, said former Texas Gov. Rick Perry. Roy Cohn, the eminence grise behind Sen. Joseph McCarthy, was a Trump mentor, so the resemblance may not be coincidental.

There’ve now been 70 attacks or thwarted plots by homegrown jihadis. Abdulazeez’s was the eighth this year. Since 2008, Mr. Perry says, illegal immigrants have been charged with nearly 3,000 homicides in Texas alone. I think Mr. Trump has risen so high so fast chiefly because he’s about the only prominent person who says what ordinary Americans think about this.

Some Democrats and left-wing journalists downplay these murders. Timorous Republican leaders in Congress have done nothing meaningful to protect Americans from them. It wasn’t until after Mr. Trump raised the issue that legislation was introduced to withhold federal funds from “sanctuary cities.”

Donald Trump has said fewer untrue or mean-spirited things than Barack Obama utters in a typical day. His GOP critics should keep that in mind.