They came for John Cunningham on a sunny evening last week, showing up at his house in Brighton like early dinner guests.

They were federal immigration agents, and they were there to throw John Cunningham out of the country he has called home for 18 years.

John Cunningham, 38, has an electrical contracting business. He has paid taxes. He has done much to improve the lives of those around him.

But what he does not have is a green card, and so the federal agents brought him to the jail in South Bay and put him in a cell with the rest of the common criminals. Because in Donald Trump’s America, that’s what John Cunningham is, a common criminal.

Now this would come as a great surprise to the young people that Cunningham helped as chairman of the Gaelic Athletic Association in Boston. It would come as a shock to the many immigrants, not just the Irish but those from other countries, that Cunningham has helped over the years. It would come as an insult to a very kind priest named Dan Finn, who runs the Irish Pastoral Center in Dorchester and who knows that John Cunningham is a good man.

Chris Lavery, Cunningham’s lawyer, told me there is no underlying criminal charge. Cunningham was grabbed for overstaying the 90-day visa he received 18 years ago.

Lavery was trying to determine whether Cunningham missed a court hearing after a customer filed a complaint that Cunningham took and cashed a deposit check for more than $1,000 for electrical work he didn’t perform. That would have produced a warrant for his arrest, but not by immigration agents.

“You would think a guy like him, with no criminal convictions, would not be a priority,’’ Lavery said.

But the days of immigrants who kept their noses clean not having to worry about being deported are gone. Under the Trump administration, Immigration and Customs Enforcement agents have been very active. And ordinary, hard-working, tax-paying immigrants are being targeted the same as hardcore criminals.

In the midst of all this round-’em-up-and-throw-’em-out talk, a question has to be asked: What is gained by arresting, detaining, and deporting someone like John Cunningham?

“Nothing is gained but ruining a good man’s life,’’ said Sean Moynihan, head of a Boston consulting firm called The Moynihan Group. “John makes this city, this state, this country better. So how is throwing him out helping anyone?’’

Cunningham is widely known in Boston’s Irish ex-pat community. He was a fixture at the Gaelic Athletic Association fields at the Irish Cultural Centre in Canton. He was especially proud of getting more kids from all backgrounds playing the traditional Irish games of hurling and Gaelic football.

It is because of Cunningham’s prominence in that community that his arrest has sent shivers through it.

“If they’ll go after John Cunningham, they’ll go after anybody,’’ said Ronnie Millar, the executive director of the Irish International Immigrant Center in Boston. “John is so well-known and so well-liked. If John Cunningham is not safe, no one is safe.’’

That is a new reality that is hitting not just the Irish, but other immigrant communities from East Boston to Lawrence, from Worcester to Springfield, and everywhere in between. Being a good person means nothing. Round ’em up.

Kieran O’Sullivan, an immigration counselor at the Irish Pastoral Center, said Cunningham was among several Irish people detained this month. Like Millar’s organization, his has been inundated with frantic, worried calls, especially as word of Cunningham’s arrest spread. He spoke with a couple that is making contingency plans for what to do with their children if they’re arrested.

“People are nervous about going to work,’’ O’Sullivan said. “What to do if both parents are picked up. This is driving people further underground. It’s a very difficult time. We need to move away from viewing immigrants as a threat to this country.’’

Fat chance that will happen with a new administration being cheered on by a sizable portion of Americans that does indeed view immigrants as a threat to this country.

O’Sullivan likes to remind people that 60,000 immigrants are serving in the American military. Members of his family from Kerry have been part of immigration waves going back to the 1950s, serving in every major US war since Korea.

“Our country would be more secure if people are allowed to come out of the shadows,’’ O’Sullivan said.

John Cunningham was just out of his teens when he came to Boston from Donegal. Like a lot of young Irish, he quickly found work, a Gaelic football team, and a supportive ex-pat community in and around Boston. He never went back to Ireland, not just because Boston was his new home but because he knew if the immigration authorities realized he had overstayed his 90-day visa, he’d be barred from the United States for at least 10 years.

He would have done anything, paid anything to obtain legal status, but he couldn’t. The same government that gladly gave him a tax ID number wouldn’t give him a way to get legal. Cunningham worked for years lobbying for immigration reform, trying to create a system that would allow millions of immigrants to legalize their status.

Some worry that Cunningham’s willingness to speak publicly about the need to reform the immigration system made him an easy target for that same flawed system.

Chris Lavery, his lawyer, visited him in jail, hard by the Expressway. Cunningham is despondent. He has spent half his life here.

He’s in lockdown most of the time. It’s unclear how long he will be held before he’s deported. He has no right to a hearing because of the visa waiver program under which he entered the country.

“What does this accomplish?’’ Chris Lavery asked.

The short answer is it accomplishes nothing. For those who would ask, “What part of illegal don’t you understand,’’ I’d ask, “What part of pointless don’t you understand?’’

John Cunningham hails from a small, beautiful place in southwest Donegal called Glencolmcille. It is an Irish-speaking area, and it’s named after St. Columba, the Irish missionary who brought Christianity to Scotland.

If St. Columba came to this country today and needed more than 90 days to spread the word of God, he wouldn’t be called a saint. He’d be called a criminal.

Kevin Cullen is a Globe columnist. He can be reached at cullen@globe.com.