Amid threats to assassinate, hang, lynch, expel and otherwise silence her, Maxine Waters clambered on to a stage in Los Angeles last week and did what comes naturally: hurl defiance.

“All I have to say is this: if you shoot me, you better shoot straight,” she told cheering supporters. “There’s nothing like a wounded animal.”

It was typical audacity from one of the most outspoken members of Congress, a 79-year-old political veteran from California who is leading the charge against Donald Trump and now finds herself at the heart of a debate about civility – or the lack of it - in political discourse.

Waters was one of the first Democrats in Washington to call for Trump’s impeachment after his inauguration in 2016, calling him a scumbag, immoral, indecent and inhumane. She branded his staff the “Kremlin Klan”.

The former factory worker now leads calls to confront and shame his cabinet members over the separation of immigrant families. People are going to “harass” and “turn on them”, be it in stores, restaurants or gas stations, she declared last month. “We’ve got to push back.”

Remember when I said Trump & his allies are scumbags? Trump is an immoral, indecent, & inhumane thug. He loves Putin, genuflects for Kim Jong-un, loves killer Duterte, wants to be in power for life like Pres. Xi, & is willing to sacrifice children. He needs 2B stopped. Impeach45 — Maxine Waters (@RepMaxineWaters) June 20, 2018

To progressive supporters, Waters is “Auntie Maxine”, a matriarchal rebel who inspires resistance to tyranny. Millennial fans have taught the grandmother terms like “woke” and “throwing shade”. Her soundbites go viral, become memes and end up on T-shirts.

To rightwing foes, she is Kerosene Maxine, Crazy Maxie, Dirty Waters and worse – Twitter spews slurs by the hour. Trump has set the tone by calling her an “extraordinarily low IQ person” and making a veiled threat: “Be careful what you wish for Max!”

The backlash reached new intensity this week.

Death threats deemed credible prompted Waters to suspend scheduled appearances in Texas and Alabama until security can be beefed up.

A conservative group, Judicial Watch, filed an ethics complaint with the House of Representatives, claiming Waters had incited mob violence against Trump supporters (she denies that and says Trump is the inciter of violence). Social media spread a fake report, purportedly from CNN, claiming Waters wanted an undocumented migrant appointed to the supreme court.

In a renewed attack, Trump called her corrupt, crazy and, along with the House minority leader, Nancy Pelosi, the face of the Democratic party. “Her ranting and raving, even referring to herself as a wounded animal, will make people flee the Democrats!” he tweeted.

It wasn’t just Republicans piling on. Some Democratic leaders also rebuked Waters for advocating harassment of Trump officials. “Unacceptable,” said Pelosi, without naming her colleague. “Not American,” said Chuck Schumer, the Senate minority leader.

This prompted a counter-blast from nearly 200 black female leaders – activists, pastors, academics, elected officials – who accused the Democrats of failing to protect Waters.

Denzel Gordon, a tourist from New York, in Los Angeles: ‘She’s doing things a lot of politicians wish they could do.’ Photograph: Rory Carroll/The Guardian

Whatever clouds hovered over her in Washington, this week it was only sun – with a looming heatwave - in Waters’ 43rd congressional district, a Democratic bastion of African American, Latino, white and Asian communities in south LA.

“She’s a headstrong woman and that’s always a positive,” said Alvarette Valley, 45, a healthcare worker, seeking shade in Inglewood, near the LAX airport. “We’re at a point where we are so far beneath being civil. Trump can spew his evil and she can spew truth about that.”

Illya Brantley, 36, a salesman, called Waters a beacon. “We have a racist-ass president. We have policies that are helping the top 1%. If you sit back and say nothing, nothing changes. A closed mouth don’t get fed. She’s harnessing energy and directing feelings.”

Locals and tourists alike at Roscoe’s House of Chicken and Waffles, a soul food restaurant, echoed the support. “She’s doing things a lot of politicians wish they could do,” said Denzel Gordon, 24, a social worker from New York. “She has the balls.”

Death threats, Trump taunts, Democratic leadership rebukes, love from the base – quite a few days, then, for Maxine Moore Waters. Those who know her well aren’t surprised. It’s been quite a life.

“She has been consistent and persistent,” said Carolyn Fowler, a member of the Black Women’s Forum, which Waters founded. A regimen of swimming and fasting keeps her going – “that and the injustice she sees on a daily basis”.

The fifth of 13 children, Waters was raised by a single mother in St Louis, Missouri. Ambition appeared to burn early – her high school yearbook reportedly predicted she would become speaker of the House.

After moving to Los Angeles in 1961, she worked in a clothing factory before qualifying as a teacher, obtaining a sociology degree and winning a state assembly seat in 1976.

‘She has been consistent and persistent,’ says Carolyn Fowler of the Black Women’s Forum. Photograph: Paras Griffin/Getty Images for Essence

She took strong, sometimes controversial positions: divesting state pension funds from businesses linked to apartheid-era South Africa; calling the 1992 Rodney King riots a “rebellion”; assailing the invasion of Iraq; accusing Barack Obama of neglecting African Americans. The Tea Party, she said, could go “straight to hell”.

Being nicknamed Kerosene Maxine – that dates from a 1994 contretemps in Congress - did not dent her rise up the ranks: chair of the Congressional Black Caucus, ranking member of the committee on financial services.

“She’s not just some liberal firebrand who doesn’t get things done,” said Fernando Guerra, director of Loyola Marymount University’s Center for the Study of Los Angeles. “She’s an incredibly experienced legislator and tactician. I believe she is the most senior elected official in the whole region at the federal, state or local level. She’s an icon.”

Corruption allegations, however, have cast a shadow.

Close relatives made more than $1m through business ties to companies and individuals that Waters aided, the Los Angeles Times reported in 2004.

Perceived conflicts of interest and nepotism prompted a liberal watchdog group, Citizens for Responsibility and Ethics in Washington, to include Waters on a list of corrupt members of Congress.

In 2008, Waters helped a bank, OneUnited, seek federal aid. Her husband, Sidney Williams, a former NFL player and ambassador to the Bahamas, risked losing $350,000 if it collapsed. After a three-year investigation, the House ethics committee exonerated Waters in 2012.

Her softening towards the financial services industry, which she used to assail, gave progressives further pause.

Come Trump, such concerns evaporated.

Waters, with her impregnable political base in LA, let rip during the primaries and never stopped. Trump, she said, was a “bully, an egotistical maniac, a liar”. She boycotted his inauguration, telling MSNBC: “I don’t honor him. I don’t respect him. And I don’t want to be involved with him.”

James Fugate, a bookstore owner, says Trump’s attacks highlight the need for firm opposition. Photograph: Rory Carroll/The Guardian

The more Trump policies caused outrage – the travel ban, dismantled environmental protections, deportations, family separations – the louder progressives cheered Auntie Maxine.

The more Trump supporters hit back – Bill O’Reilly compared her hair to a “James Brown wig” and a conservative magazine called her the “poster child for Trump Derangement Syndrome” – the more Waters’ supporters had the same thought: pass the kerosene.

“She won’t back down and she shouldn’t back down,” said Jewett Walker, a Baptist pastor who ran local political campaigns in and around Waters’ district. “Because she has dared to criticise Trump, he has demonised her in the worst way and made her a target for zealots.”

James Fugate, who runs a bookshop in south LA, said Trump’s “low IQ” taunts showed the need for vigorous opposition. “He’s figured out a way to come close, without actually saying it: ‘Oh, she’s a monkey out of the tree.’”

The concern for Democrats is whether Auntie Maxine’s recipes, such as publicly shaming Trump officials, will backfire by alienating swing voters and galvanising Republicans in November’s midterm elections.

Guerra, the political analyst, played down that risk, saying the challenge for Democrats was to fire up their own base. “If you turn out Democrats, they win. Without Maxine Waters and people like her, the Democrats cannot recapture the House.”