“The president’s inflammatory rhetoric is counterproductive to the goal that we the people, including new arrivals in America, seek—to live in peace, security and happiness and to eradicate MS-13”, says the author.

I applaud President Trump’s mission to combat MS-13. The gang must be disrupted, dismantled and defeated. There should never be any disagreement about that, and presidential involvement is incredibly beneficial.

MS-13 members are ruthless and depraved. The gang models itself on organized crime syndicates throughout history. It is a murderous and destructive force in too many good communities across America, including Long Island, where I’m from.

But Mr. Trump’s failure to distinguish properly between MS-13 members and other immigrants, along with his divisive, discriminatory language, particularly against immigrants from Latin America, hampers efforts to rid our communities of MS-13. The president’s inflammatory rhetoric is counterproductive to the goal that we the people, including new arrivals in America, seek—to live in peace, security and happiness and to eradicate MS-13.

During my tenure as mayor of Glen Cove, N.Y., we enjoyed the lowest crime rate of any community with more than 20,000 people on Long Island. My city is a mashup of immigrants and multigenerational families. We achieved public safety and harmony by relying on two fundamental American credos.

First, all men and women are created equal. Not “all men and women with U.S. passports or green cards.” All human beings are entitled to the same respect and dignity. Issues from public safety to immigration reform cannot become an excuse for racism or other forms of discrimination.

The second credo is “all men and women are equal under the eyes of the law.” If you live in America, whether you are a newcomer or a descendant of the Pilgrims, you must obey the law.

And that’s where our 45th president’s words and actions become problematic. To protect those who obey the law, and to take down those who break it, particularly members of MS-13, community policing is central.

The key to community policing is a healthy, respectful and productive relationship between police officers and the community they are sworn to serve and protect. Mr. Trump’s approach—his sweeping rhetoric that lumps all immigrants together, his proposal to curtail legal immigration drastically, his failure to support a bipartisan permanent fix for beneficiaries of Deferred Action for Childhood Arrivals, his elimination of temporary protection status safeguards—amounts to a war on immigrants, a war far beyond MS-13, which has a chilling effect on police-community relations with Latinos in America.

Police must be able to work with law-abiding people to identify MS-13 members and movements in their communities. While overseeing police departments as Glen Cove mayor and Nassau County executive, I saw community-policing stop MS-13 in its tracks. During my time as executive, Nassau was the safest county of more than 500,000 inhabitants in the U.S.

In contrast, when people are afraid to cooperate with the police because of Mr. Trump’s words and his administration’s crackdown on Latino immigrants, local leaders in the fight against MS-13 are pushed into the shadows. It’s a tragedy when people are afraid of the police and of government in general—afraid of reprisal from the officials every American relies on for protection.

My grandfather and father were immigrants from Italy. As a first-generation American, I could not be prouder or more inspired by their success as newcomers to this great nation. I am also keenly aware of how the criminal actions of a sliver of Italian immigrants were once used to disparage and deny opportunity to all Italian newcomers to America in the first half of the 20th century.

We cannot make the same mistakes by equating MS-13 with law-abiding immigrants from Latin America. Sadly, Mr. Trump—on a near daily basis—careens down this dangerous and destructive path. The president should put divisive language aside, support law-abiding immigrants, and make community policing more effective. And then he needs to be open to common-sense solutions for the DACA crisis and for comprehensive immigration reform.

(Mr. Suozzi, a Democrat, represents New York’s Third Congressional District)