The nation’s homeland security chief had a stern message to presidential candidates and other politicians on Wednesday: Tone it down.

Homeland Security Secretary Jeh C. Johnson made his plea while appearing at a conference hosted by Latino lawmakers.

“All of us in public office, those who aspire to public office and who command a microphone owe the public calm, responsible dialogue and decision-making,” Johnson said. “Not overheated, over simplistic rhetoric and proposals of superficial appeal. In a democracy, the former leads to smart and sustainable policy. The latter can lead to fear, hate, suspicion, prejudice and government overreach. These words are especially true in matters of homeland security and they are especially true in matters of immigration policy.”

As evidence, Johnson cited a 2013 Pew Research poll that asked Americans whether the number of immigrants illegally entering the United States was higher, lower or about the same from a decade ago. Fifty-five percent of respondents said it was their perception that there was more illegal immigration, he said. But government figures show that illegal border entries have declined over the past several years.

While illegal border entries by migrants coming from Central Americans have increased in the past three months, Johnson said that apprehensions along the U.S.-Mexico border have dropped overall to levels not seen since the early 1970s.

Johnson spoke Wednesday at the annual conference of the Congressional Hispanic Caucus Institute, at the Washington Convention Center. He has made his plea for political civility before, but conceded that an increased focus on the 2016 presidential campaign is likely to draw more attention to his request. The secretary never mentioned presidential candidates by name, but discounted a controversial proposal backed by Republican presidential front-runner Donald Trump.

“Building a wall across the entire Southwest border is not the answer” to illegal immigration, he said to cheers from the crowd.

“Notwithstanding the political rhetoric, we are not going to deport 11 million people,” he added later. “We’re not going to deport a population equal in size to New York City and Chicago. They live among us, we know them, they’re becoming integrated members of society.”

Trump and other GOP candidates support building a wall along the entire span of the U.S.-Mexico border and have called on federal agencies to apprehend and deport the estimated 11 million to 12 million undocumented immigrants living in the United States.

But Johnson said that instead the federal government should invest more in “technology for border security.” He also noted that immigration agencies have increased “in-country processing” in Central America, allowing people in the United States to more easily and safely apply to bring their children or spouses into the country. And he renewed the Obama administration’s calls for Congress to include a $1 billion aid package for Guatemala, El Salvador and Honduras in the next spending bill.

The aid package is critical, he said, to help address “underlying causes of illegal migration from Central America.” He cited recent visits to immigrant detention centers in the southwest, where he has met with the families or young children who have illegally crossed the border. He recounted the story of a 7-year old girl who had come alone in hopes of reuniting with her mother.

“The unaccompanied kids is a heartbreaking phenomenon, so we can put a lot on the border, we can put a lot of my people on the border, the governor of Texas can put a lot of people on his border, but that doesn’t address the underlying problem in these countries,” he said.

Johnson also took questions in a brief session moderated by Rep. Luis Gutierrez (D-Ill.) an outspoken immigration-reform advocate. While Gutierrez has been a vocal critic of the Obama administration’s immigration policies, the congressman and secretary have developed a close personal bond in recent years, which was evident on stage.

Answering questions from the crowd, Johnson defended Operation Streamline, a Justice Department program in Arizona criticized by many immigration advocates and said that Immigration and Customs Enforcement is preparing to shutter some immigration detention centers pursuant to a recent court order. And he admitted that he’s struggled to remind the national news media and his biggest critics that despite the rhetoric, illegal border crossings have declined.

“The national media is starting to pay attention, but we’re now in the middle of the political season, so a lot gets drowned out by the political rhetoric,” he said. “And I think it’s incumbent upon us in political office who have the microphone to give the facts, to state our views and our policies in calm, informed terms and to tell the public that our investments in border security have led to these results and to tell the public about our new policies and focus more on the felons and those who commit multiple misdemeanors or significant misdemeanors. … I’m just going to keep repeating that message. And I hope others will do the same.”