"We can't act out of fear," he told ABC News' "Nightline."
"I understand the fear," Stiller continued. "I want our country to be secure, but I think compassion and security are not mutually exclusive."
"This country has always opened its arms to immigrants, to refugees, to those fleeing persecution," he said." It's very important that we change the policy and we get back to doing what we have done."
Stiller, one of the most bankable names in Hollywood, is now lending his name to this effort –- a serious cause for a comedian who has built a career out of awkward hilarity, from the cringe-worthy zipper incident in "There's Something About Mary" to the self-absorbed male model in "Zoolander."
One of the families Stiller met with was the Salah family: Mohamed, a veterinarian, his wife Alaa, an agricultural engineer, and their two children.
"Their one son, his eyes were damaged by bombing near their home, so they're trying to get medical care for him," Stiller said. "Alaa, what she said to me was, 'We just want a chance to move forward, we just want a chance to live our lives,' and she was crying when she was saying it. She was so passionate about it."
Stiller said that, when he was at the refugee camp, they didn't have electricity, but were just getting a solar panel grid up and running.
"They didn't have toilets, no running water," he said. "They showed me their 'bathroom' [area] was like a plastic cup with four toothbrushes in it."
When asked about the concerns that terrorists could be among the refugees being allowed into the U.S., Stiller pointed to the extreme vetting process already in place.
Then on Feb. 3, a judge in Seattle blocked President Trump's order temporarily, which opened the doors once again to family members caught in the middle of a legal showdown between the White House and the courts.
Over the weekend, the president's lawyers appealed the Seattle judge's ruling. Trump tweeted, "The opinion of this so-called judge, which essentially takes law-enforcement away from our country is ridiculous and will be overturned."
Hours later, Trump tweeted again, writing, "Because the ban was lifted by a judge, many very bad people may be pouring into our country. A terrible decision."
ABC News Chief legal analyst Dan Abrams spoke to this issue of the executive branch seeming to undermine the judiciary branch.
"I think it's OK to say, 'I disagree with this judge,' I think it's OK to say, 'I think this is a horrible decision.' But to say, 'so-called judge,' suggesting the judge is illegitimate, that's where you get into scary territory, where it sounds like the president is saying that the courts are either illegitimate or shouldn't matter."
Early Sunday, the president's appeal was rejected and some think the case could go all the way to the Supreme Court.
"If the administration had come forward with a more detailed, well-thought out order, I think they might be in better shape right now," Abrams said. "The president does have enormous autonomy when it comes to immigration."
President Trump has bashed Hollywood in the past for speaking out on this cause, saying that they are not experts on the matter. Stiller said he found the comment "kind of ironic."
"I don't want to criticize the president, he's the president," Stiller said. "I think it's ironic because obviously he himself is a celebrity. But to me it's a greater issue, now that he's the president and leader of the free world. I think America has to set the example and we always have with refugees."
On Monday, in a joint declaration to the federal appeals court against the executive order, several former national security officials said, "Since September 11, 2001, not a single terrorist attack in the United States has been perpetrated by aliens from the countries named in the Order." The U.S. Court of Appeals for the 9th Circuit today will hear arguments for and against the president's travel ban.
"If you really look at the record of terrorist violence in America for the last 15 years, none of it relates to refugees," Stiller said. "I think this idea of refugees coming into our country equals, as the president has said in a tweet, 'death and destruction,' is just wrong."
Stiller said now that he has found his political voice, he plans to keep speaking out for those who can't.
"I think it's really unfortunate that it's become politicized because it is a humanitarian issue. I mean, that's the bottom line," he said. "These are people's lives and our country has always been a place that accepted people who are fleeing from persecution and war and that's who we are as a country."