The quintessential Ugly American arrived in England on Monday, where it didn’t take long for him to hurl insults at London’s mayor. But presumably his mood will be lightened by the absence of any American vessels bearing the name John McCain.

The Pentagon confirmed that a Trump flunky in the White House ordered the Navy to keep the USS John McCain “out of sight” when Trump visited Japan last week, to protect the president’s eggshell ego and minimize the odds of a meltdown. A normal commander-in-chief — armed with an adult sensibility and mindful of the military’s nonpartisan tradition — does not need to be coddled that way, but, as we know by now, this particular guy routinely puts petty above country.

Indeed, Trump has defended the unnamed aide’s McCain-dissing directive: “Somebody did it because they thought I didn’t like him, OK? And they were well-meaning.” (Trump dislikes McCain, but he likes Kim Jong Un, who murdered his own uncle. Think about that.)

And on Sunday’s “Meet the Press,” acting White House chief of staff Mick Mulvaney marched in lockstep: “Some 23 or 24-year-old person on the advance team went to that site and said, ‘Oh my goodness, there’s the (USS) John McCain, we all know how the president feels about the former senator, maybe that’s not the best backdrop, can somebody look into moving it?’ That’s not an unreasonable thing to ask.”

Actually, it was an outrageous thing to ask. Acting Defense Secretary Patrick Shanahan said he would never have authorized a request to limit the visibility of the Navy destroyer (which was named for McCain’s grandfather, a Navy admiral). More importantly, Shanahan sent a message to the White House “that the Department of Defense will not be politicized.”

That’s the fundamental issue here. Trump is free to stew on his own time about McCain — the war hero and POW who didn’t plead bone spurs to avoid Vietnam service — but, according to a 200-year tradition and specific Defense Department guidelines, Trump is not free to bend the nonpartisan military to his partisan whims. He is not free to demand personal loyalty or to indulge personal grudges.

But that’s been his pattern all along. He signs MAGA caps at military installations, welcomes Trump campaign banners at military events, and as far back as the Armed Services inaugural ball in January 2017, he told active service members: “I like you for a lot of reasons. I like the fact that you all voted for me, right? You all voted for me!”

Trump fans and servile Republicans naturally don’t care, but Trump’s behavior seems a lot more dire than the 2014 incident when President Obama saluted a Marine guard while holding a coffee cup. (The Republican National Congressional Committee went ballistic: “Wait — did President Obama just salute the Marines with a LATTE in his hand?!”)

In the words of Diane H. Mazur, a former Air Force munitions officer and law professor, Trump’s behavior is “beyond-the-pale inappropriate … politicizing the military for a president’s personal benefit and vanity. Military professionalism depends on strict political neutrality. A president who openly fishes for votes and affirmation from people sworn to obey his orders will destroy that careful constitutional balance.”

And the U.S. Supreme Court defended that balance in a 1976 ruling. Four of the six majority votes were cast by Republican appointees. The court stated that the military has a constitutional responsibility to avoid “both the reality and the appearance of acting as a handmaiden for partisan political causes or candidates,” and to keep “official military activities…wholly free of (partisan) entanglements,” in accordance with “a 200-year tradition of keeping the military separate from political affairs.”

A White House aide — a “23 or 24-year-old,” according to Mulvaney — who’s tasked with managing Trump’s moods is not likely to know such things. But a White House that’s worthy of this country would intuitively understand that all Navy destroyers within the Seventh Fleet are created equal, even the one that bears the name McCain.

At the senator’s funeral last September, ex-President George W. Bush said, “John detested the abuse of power…John’s voice will always come as a whisper over our shoulder: We are better than this. America is better than this.”

Only if we can prove it in 2020.

Dick Polman is the national political columnist at WHYY in Philadelphia and a “Writer in Residence” at the University of Pennsylvania. Email him at dickpolman7@gmail.com.