In a political season marked by livid constituents railing at their representatives during town hall meetings, an event on Saturday in Houston was positively mellow by comparison. But then, the topic was not a divisive issue such as healthcare. It was the impeachment of Donald Trump.

The meeting was held by Al Green, a 69-year-old Democratic Houston congressman who took office in 2005 and is typically softly-spoken and understated. Not on Wednesday, though, when he became the first member of Congress to take to the floor and ask for the president’s impeachment.

“I rise today, Mr Speaker,” he said, “to call for the impeachment of the president of the United States of America for obstruction of justice.”

It was a move that thrilled many liberal activists, though it was not immediately endorsed by many of Green’s colleagues, who worry that rhetoric is outpacing reality so soon in Trump’s tenure, with Republicans controlling both the House and the Senate and much left to be proven amid the miasma of revelations and accusations.

Green said Trump’s decision to fire James Comey last week as FBI director amid the bureau’s examination of possible collusion between the president’s campaign and Russia justified his decision.

“It’s not too soon,” he told the Guardian on Saturday. “When the act is committed, from that point forward the impeachment can begin at any moment. So the president committed an impeachable act when he fired the FBI director who was investigating him. That’s pretty strong evidence.”

He added that poll numbers will indicate how fast the impeachment bandwagon rolls, with politicians likely to follow the will of the people.

“When the American people decide they’ve had enough,” he said, “at that point you’ll see a different attitude. My hope is it will start sooner rather than later.

It's about democracy not Democrats; it’s about the republic not Republicans ... you can't allow anyone to be above law Al Green

“I will file, if no one else does, an impeachment resolution. It’s filed in the name of the people of the United States of America. I will do it. It’s not my desire to do it, it’s not something that I want to do, but I’m going to also wait to see what the American people are going to do – this is something that will start from the ground up, not the top down.”

Green denied he is grandstanding: “It surely wasn’t because I expected a big parade, it was simply because I understand the constitution, I understand that this is an injustice, and I firmly believe that this is about democracy not Democrats, it’s about the republic not Republicans; I firmly believe that you cannot allow anyone to be above the law.”

The law was a pronounced presence on Saturday. In a crowd of 150 to 200 people at a church hall in south-west Houston, there were a dozen police officers, six private security workers to screen everyone at the entrance and a bomb-sniffing dog.

Green, who is black, received threats after his speech in Washington. He began Saturday’s meeting by playing a couple of racist messages left on his office voicemail. The callers used racial slurs and made references to lynching. In another, posted online by his assistants, a man says: “You called for the impeachment of our wonderful, loving, United States president. You sound disgusting. God, you are so disgusting.”

Phyllis Frye: ‘I’m very proud of him, speaking up as he is for impeachment of the current president.’ Photograph: Tom Dart/The Guardian

When video of Green’s speech to Congress was shown there was warm applause. One woman asked whether he thought Mike Pence, Trump’s vice-president, should also be a target. Green said the focus must be on Trump. Another attendee expressed concern about what she saw as the politicization of the FBI.

“I’m very proud of him, speaking up as he is for impeachment of the current president,” said Phyllis Frye, an attorney, before the meeting. “The main thing that troubles me is that [Trump] doesn’t act presidential. He’s constantly, at three and four and five o’clock in the morning, tweeting all kinds of silliness. I wish they would take his phone away.”

Vivian Lee, a peer counselor at the Houston Center for Independent Living, said Trump should be impeached “if he gets any worse, yeah. And I don’t see it getting any better before it gets any worse. Once the healthcare act falls apart then we’ll have people who will literally die because they will not have insurance.”

Her group helps people with disabilities find housing. Budget cuts and uncertainties related to federal funding, she said, are affecting lives. The Trump administration is proposing increasing military spending while pruning the budgets of many other government departments.

“We have 900 families in the city of Houston with nowhere to go,” she said.

For Lee, the concept of obstruction of justice is not simply about what the president’s coterie may or may not have discussed with Russians and figures in faraway Washington; it is also about government policy that impedes the civil rights of people in need that she meets on a daily basis.

“If nothing else, [impeachment] is our answer,” she said. “Because the answers we’ve been given don’t make you feel any better – I mean that he’s taking money from housing and education and medical to fund a war that we don’t need. I need local answers.”