Sean Penn: Rebel with a cause

He's the Hollywood star turned activist who's riled people throughout his career. And now the British are in his sights

What was Sean Penn doing in Argentina anyway?

Why are a movie actor and his moustache touring South America like visiting statesmen, and being welcomed with a press conference by each of the continent's presidents? Actually, as it happens, Penn is there as a visiting statesman: in January, he was appointed Haitian ambassador-at-large, the first time a non-Haitian has ever been awarded such a title.

Not that this necessarily qualifies him to comment on the status of disputed archipelagos in the South Atlantic. Indeed, you might argue that to wade into the debate over the Falkland Islands – or "the Malvinas of Argentina", as Penn appears to prefer – is a distraction from his task. Nevertheless, after meeting Argentinian leader Cristina Kirchner this week, the actor informed a crush of journalists that "the world today is not going to tolerate any kind of ludicrous and archaic commitment to colonialist ideology".

Later, in Uruguay, he disparaged the RAF's plans to post Prince William to the islands as "unthinkable". The reactions of right-leaning British MPs and media outlets were predictable. Tory Patrick Mercer, a former army officer, called Penn's comments "moronic". The Daily Mail complained that "the achingly trendy ex-Mr Madonna" was "shooting his mouth off". Falklands War veteran Simon Weston called him an "idiot". Even mild-mannered Countryfile presenter Ben Fogle suggested he should be fed to crocodiles.

More remarkably, Penn's contribution inspired a brief surge of seething patriotism in even those UK citizens who wouldn't normally give a second thought to the far-flung colony. (Or should that be "self-governing British Overseas Territory"?) That is the unifying power of the tedious Hollywood liberal – and Penn is perhaps the most committed of all to the ludicrous and archaic ideology of celebrity interventionism. He has previously, for example, inserted himself into arguments surrounding Iran, Iraq and Venezuela – though, to his credit, he did visit those places before broadcasting his views.

Politics entered the life of Penn's father Leo uninvited. An actor like his son, and a decorated Second World War airman, Leo was among those blacklisted by the House Un-American Activities Committee during the 1950s for refusing to testify against his peers. Thanks to his progressive sympathies, he found himself unemployable in film, and turned to the New York theatre for work, where he met Penn's mother, Eileen, also an actor. After Michael, the first of their three sons, was born in 1958, the couple moved to Los Angeles, where Leo became a television director.

Sean was born in August 1960, and claims his kindergarten teacher christened him "Gary Cooper" for his silence and surliness. He was a volatile teenager, arguing persistently with Eileen, from whom he is said to have inherited his hard edges. In 1974, he made his first screen appearance in an episode of Little House on the Prairie, directed by his father. He grew up in the company of actors, including his younger brother, Chris, and friends Charlie Sheen and Emilio Estevez. Like them, he first emerged as part of the so-called "Brat Pack", appearing with Tom Cruise in Taps (1981), and as the dope-smoking surfer Jeff Spicoli in Fast Times at Ridgemont High (1982).

Even during this first stage of his career, Penn was known as a formidable on-set presence. He had spent two years training intensively with method acting coach Peggy Feury and, to prepare for his role, lived out of a car at the beach during the filming of Fast Times. It helped that he had grown up surfing, and that the Vans trainers made famous by Jeff Spicoli came from his own shoe collection.

Penn soon became a tabloid favourite, too, and after a brief engagement to the actress Elizabeth McGovern (now best known as Lady Grantham in Downton Abbey), he wed the young pop star Madonna in 1985. Enraged by press helicopters hovering low over the ceremony in Malibu, he found a gun and started firing at them. The marriage proceeded in similarly tempestuous fashion: while the couple were shooting their 1986 turkey Shanghai Surprise together in Macau, Penn came across a photographer snooping in their hotel room, dangled the man from a ninth floor balcony by his ankles, and was arrested for attempted murder. He escaped from jail and fled the country on a jetfoil. In 1987, he was sentenced to 60 days in jail for assaulting one of his wife's more ardent fans. The couple divorced in 1989, when Penn was charged with domestic assault, after tying Madonna to a chair and beating her.

His second marriage appears to have been troubled, too, if less spectacularly so. Penn and the actress Robin Wright had a daughter in 1991, and a son in 1993, marrying in 1996. But they endured a number of separations and abortive divorce filings before separating permanently in 2010.

Unhappy with acting, at the start of the 1990s Penn had stepped back from the screen and moved behind the camera. His directorial debut, The Indian Runner, appeared in 1991. His subsequent films, The Crossing Guard (1995) and The Pledge (2001), shared its melancholy vision. The Indian Runner, based on a track from Bruce Springsteen's Nebraska LP, concerned two warring brothers and, according to Penn's childhood friend Matt Palmieri, reflected the warring halves of its creator's character. "One part of [Sean] is the responsible, clear-headed, thoughtful older brother, the guy who kind of takes charge in a crisis," Palmieri told The New Yorker. "On the other hand, he's angry, wild, rambunctious – definitely highly aggressive."

When he returned to acting in earnest, it was to great acclaim. He was nominated for an Oscar in 1995, for his turn as doomed Death Row inmate Matthew Poncelet in Dead Man Walking, and finally won his first Academy Award in 2004 for the crime drama Mystic River. Critic John Lahr described the two performances as being "among the high-water marks of contemporary acting". Penn won again, for Milk, in 2008. By then, he was also well known for his politics. In the run-up to the Iraq war, he spent $56,000 publishing an ad in The Washington Post, criticising George W Bush. He visited Iraq before and after the 2003 invasion. In 2005, he travelled to Tehran to write 12,000 words for the San Francisco Chronicle. He visited Venezuela to meet Hugo Chavez in 2007, and to Cuba for an audience with Raul Castro in 2008.

The actor's humanitarian activities may have started with mere curiosity – in 1992 he drove into LA's Rodney King riots to take a closer look, and had a shopping trolley thrown through his windscreen – but they became hands-on. Following Hurricane Katrina in 2005, he flew to New Orleans, found a boat and started fishing victims from the floods personally. When Haiti was hit by a monstrous earthquake in 2010, he swooped into the country with $1m in funding and no NGO experience, and founded the J/P Haitian Relief Organisation. A year later, he was still there, running the Pétionville tent camp, population 55,000, on the golf course of a former country club.

Penn's personal immersion in Haiti ameliorated the impression that many Americans had built up over the preceding decade, of – as The New York Times put it – a "tiresome pinko bloviator". His politics put aside, he won many admirers among those disillusioned with the NGO community. Brad Horwitz, Haiti's largest US investor and a J/P HRO supporter, told the newspaper: "Sean's politics and mine are completely opposed. His go left, mine go right. But politics are kind of irrelevant in this... and J/P HRO have shown real staying power."

British detractors beware: Penn does not respond well to sneers. Last year, for instance, he told CBS News that he hoped his critics would "die screaming of rectal cancer". When the makers of South Park mocked Penn and his fellow Hollywood liberals in their film Team America, he wrote an open letter inviting them to join him on a road trip to Fallujah and Baghdad, signing off "All best, and a sincere fuck you". He is perfectly comfortable making enemies. "I love humankind; I don't like humans," he has said. "I don't get along with people very well. I never did."

A life in brief

Born: Sean Justin Penn, 17 August 1960, Los Angeles County, California.

Family: Second of three sons of actor and director Leo Penn and actress Eileen Ryan. Married to Madonna 1985-89, then to actress Robin Wright in 1996, with whom he has two children. They divorced in 2010.

Career: Made his film debut in 1981 in Taps. Appeared in more than 40 films including Dead Man Walking, I Am Sam, The Thin Red Line, Sweet and Lowdown and 21 Grams. Nominated for five Oscars and won best actor twice, for Mystic River and Milk. He was vocal in his opposition to George W Bush and the Iraq war, and was heavily involved in the aftermath of Hurricane Katrina and the Haiti earthquake.

He says: "I'm a person that feels pretty alienated from the rest of the world and never felt understood by anyone."

They say: "What on earth has this got to do with Sean Penn? He's neither British nor Argentine and seems to know nothing about the situation." Patrick Mercer MP