WASHINGTON — My brothers Michael and Martin attended baseball’s opening day at the old Griffith Stadium in April 1951, with the Senators (as our team was then called) playing the Yankees. President Harry Truman had been invited to throw out the first pitch, and the stadium erupted in boos; Truman had just fired the extremely popular Gen. Douglas MacArthur as commander of the Far East, and the crowd was irate.

When the boys got home, Martin confessed to our father that he had stood up to boo the president before Michael pulled him down.

“Dad told me that President Truman was a great man,” Martin later recalled. “He said that if Truman fired MacArthur, he must have his reasons and that I should never boo another president. I never did.”

It seems so quaint now, the idea of respecting the president. Gallant has vanished; gladiatorial is in. Patriotism is no longer a premier American virtue. And to a large degree, we have Donald Trump and Rupert Murdoch to thank for that.

Trump always ridiculed people, but when he brought that into the presidential arena, it was like injecting a virus of cruelty into the political bloodstream.

When I flip on Fox News at night, I cringe at the way they make fun of President Biden, the sick delight they take in sniping at any perceived infirmity.

Mitt Romney brought some rare Republican rectitude to the Capitol when he was asked about Trump being held liable for sexual abuse and defamation in the E. Jean Carroll trial.

“He just is not suited to be president of the United States and to be the person who we hold up to our children and the world as the leader of the free world,” Romney told CNN’s Manu Raju. (The Utah senator also earlier chided Representative George Santos, saying, “You don’t belong here.”)

Todd Young, the mild-mannered conservative senator from Indiana, made it clear Thursday, after Trump’s brazen performance at the CNN town hall, that he’d had enough.

He told reporters on the Hill that he would not be supporting the former president as the Republican nominee. Asked why, he replied, “Where do I begin?” — a bracing echo of Joseph Welch’s “Have you no sense of decency?” line to that earlier bully boy Joe McCarthy.

As a video circulates of Trump celebrating his CNN performance by dancing to “Macho Man” by the pool at Mar-a-Lago, we see Trump unplugged. The existential threat is aiming to get back in the Oval, this time without anyone trying to keep him from going completely off the rails, and with the scary new world of superevolved A.I. chatbots to help him lie and smear. (Trump posted a doctored video on Friday of Anderson Cooper saying “That was President Donald J. Trump ripping us” a new one “here on CNN.”)

Trump is spiraling into even more of a self-deluded narcissist, if that’s possible. And he’s even more obsessed with numbers — if that’s possible. When he was asked by the terrific Kaitlan Collins if he regretted his actions on Jan. 6, he began rhapsodizing about, and exaggerating, the size of the crowd that day.

“I have never spoken to a crowd as large as this,” he said, adding: “They were there with love in their heart. That was an unbelievable — and it was a beautiful day.”

He called one of the most heinous days in American history “a beautiful day.” He called the Black Capitol Police officer who shot Ashli Babbitt, who was trying to break into the House chamber, a “thug.”

New Hampshire voters in the audience were cheering on Trump, and many even laughed when he crudely re-defamed E. Jean Carroll.

The town hall was enlightening — and frightening. But we needed that reminder to be on full alert, because Trump is not just an unhinged and dangerous extremist; he is also a cunning and dominating insurgent.

The argument that the media should ignore Trump and keep him under a bushel basket is ridiculous. You can’t extinguish Trump by not talking to him. He’s always going to find a platform.

Sun Tzu stressed that victory depends on knowing the enemy — “Force him to reveal himself.” Roberta Kaplan, Carroll’s lawyer, did a skillful job of letting Trump convict himself in the deposition.

President Biden needs to see what he’s up against. There are only so many times Biden can say “C’mon, man!” in a debate. The more he sees Trump in action, the less likely he is to be steamrolled. Biden’s team has been blithely underestimating the opponent. The cascading indictments allow Trump to play the gilt-dipped martyr on an even larger scale.

The task is to challenge Trump and expose him, not to put our fingers in our ears and sing “la, la, la.”

“It strikes me as fundamentally wrong to deny voters a chance to see candidates, and particularly front-running candidates, answering challenging questions from journalists and citizens in open forums,” David Axelrod told me Friday. “You can’t save democracy from people who would shred its norms by shredding democratic norms yourselves.”