Dan Janison Melville. N.Y. Tuesday January 26, 2010. Daniel Janison,

Dan Janison has been a columnist at Newsday since 2007.

Smashing the murderous and menacing MS-13 gang is a popular goal, a consensus issue, a matter of civil justice on Long Island, widely viewed as worth the effort.

Personal displays of attention to Brentwood from President Donald Trump and his attorney general, Jeff Sessions, should add up to a positive for a beleaguered Long Island community.

But, of course, it had to come with a live, televised, campaign-style exhibition. This took the form of an address to those in uniform, as Trump performed his familiar tough-talk strut.

The president said he earlier told assembled police: “Please don’t be too nice.”

“Like when you guys put somebody in the car and you’re protecting the head. You know? The way you put the hand over [the head], like ‘Don’t hit their head’ and they’ve just killed somebody, ‘Don’t hit their head.’

“I said, ‘You can take the hand away,’ OK?”

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Consider it a variation on last summer’s election gatherings, where Trump, protected by others, would shout his advice to the service personnel assigned to remove those disrupting his speeches. As in: “Get ’em outta here!”

For the preening commander-in-chief, this was clearly lighthearted fun, keyed to the audience of the day.

Rebukes and disclaimers naturally followed — from those who actually do the work of directing police agencies, including the Suffolk County police and the NYPD. Add to that the national Fraternal Order of Police, which endorsed Trump last year.

Across the past week, this one-two combo of rally-and-backlash was repeated with other institutions. For some reason, the president chose to go before the National Boy Scout Jamboree and attack President Barack Obama and Hillary Clinton, and complain about “fake news” and the electoral system.

Criticism followed from parents. So did an apology from the head of the Boy Scouts, who said it was “never our intent” for the event to unfold as a political exhibition.

By itself, attention from the president would be generally considered a good thing. It was the show that turned controversial.

Also last week, Trump held an abbreviated electronic rally of sorts on Twitter — where he abruptly announced that he was banning transgender citizens from serving in the military.

Here, too, the adults in charge reacted.

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Marine Gen. Joe Dunford, chairman of the Joint Chiefs, wrote to top brass that there would be “no modifications to the current policy” until the president sends a directive and the brass provide guidance.

“In the meantime, we will continue to treat all of our personnel with respect.”

Thus completed another one-two Trump combo, with the success of governance yet to be revealed.