There are two things people really want to know about the cartoonist Aaron McGruder. The first is precisely what he said to Condoleezza Rice, the US Secretary of State, at an awards ceremony three years ago. Rice and McGruder, 32, were both being given an award by the National Association for the Advancement of Coloured People, the oldest civil rights organisation in the country. Beforehand, McGruder had told anyone who would listen that Rice was a mass murderer (it was not long after the invasion of Afghanistan) and that he would have no qualms about telling her so to her face. With McGruder's help, rumours about their subsequent exchange became legend. "I was never as cavalier with her as I sounded," he says now. "I had a brief encounter with her and I knew I had to say something. I said something like: 'I don't want you guys to kill me so I'm just going to mind my own business.' I was eminently aware when I met Condi that she could make my whole family disappear. I have never been fearless. I've always had a healthy fear of this government."
The second is precisely how a young, left-wing African-American has managed to sell the Boondocks, a syndicated cartoon strip that combines the messages of black power and liberal-left politics, blended with hip-hop humour, to more than 300 newspapers. It's so successful that the cable channel Adult Swim turned it into its flagship television show - the most expensive in its five-year history. The risk paid off: The Boondocks cartoon premier was Adult Swim's highest-rated programme ever and the number of viewers is still growing.
At the beginning of our interview, the question of how McGruder has managed to pull this off prompts a shrug. By the end of it, he has what seems like the beginning of a thesis. "When you consider how quickly and how forcefully the extreme right came into power in the last few years - not just in terms of war but the clampdown on American journalism ... well, ultimately, some counter-voice gets through. It will always be somewhat limited and marginalised. It's just fortunate for me that my voice was allowed to continue. There is a silent majority that is opposed to the direction of the country and my strip gives them a small outlet every day to feel like they're not crazy. I keep telling people, 'Powerful corporations allow you to see that strip every day so it's not the revolution.' But sometimes it surprises me."
The Boondocks revolves around two child characters - 10-year-old Huey and eight-year-old Riley - who have moved, with their grandfather, from the southside of Chicago to a white suburb where they attend the J Edgar Hoover elementary school. Huey aspires to be a radical black revolutionary; Riley to the thug-and- gangsta life. Their grandfather just wants to keep them both under control and out of what is left of his hair.
A few of the strips that surprised many in the aftermath of 9/11 include Huey calling the FBI's terrorism tip-off line to say that he knows of many Americans who helped train and finance Osama Bin Laden. "All right, let's see," he tells the operator. "The first one is REAGAN. That's R-E-A-G ... Hello? Hello?"
Elsewhere Huey has accused the rightwing commentator Ann Coulter of being a man: "I'm just sayin' she has a pretty big Adam's apple." He has also claimed that George W Bush has probably smoked crack: "C'mon is it really that hard to believe?"
The Los Angeles Times has branded McGruder "the angriest black man in America" but, in the flesh, he seems altogether too young and too content to be even vaguely upset. The description sounds like lazy racial profiling - young black men with something to say are always described as "angry"; occasionally also "articulate", but rarely "thoughtful". McGruder doesn't take offence. "They don't have to misquote you if they want you to come off like a lunatic or smart or funny. If I don't like it, I shouldn't do the interviews."
While his political influences are clear, it is the comic and musical influences that give the strip its character and prevent it from becoming a diatribe. Along with rap groups such as Public Enemy and KRS, he cites Star Wars, Peanuts and Monty Python as having made an impact. It is an eclectic mix, in keeping with his upbringing in a very white area of suburban Maryland where he briefly went to a Jesuit school.
His parents didn't talk politics much at home but his own crystallised when he took African-American studies at the University of Maryland. There, Jayson Blair, the ambitious editor of the university newspaper, the Diamondback, gave him his first strip. Blair later became infamous for fabricating stories as a New York Times reporter.
Since McGruder has become nationally known, he has made almost as many enemies as Blair. As well as the entire Bush administration, his strip has targeted Black Entertainment Television (a cable channel), singer Whitney Houston and her husband Bobby Brown, rapper Puff Daddy and Santa Claus.
He has a knack for alienating what would seem to be natural allies in real life too. Two years ago he was heckled at the leftwing Nation Institute's annual party after he lambasted the crowd for being lame liberals and crowned it by admitting that he had voted for Ralph Nader in 2000. At that point, the Insititute's President, Hamilton Fish, told the New Yorker, "It got interactive."
McGruder also has the dubious honour of creating the strip most likely to be censored. During the Rice episode, the Washington Post pulled the strip, claiming it was inappropriate. The Post's editor, Leonard Downie, said in a statement at the time: "The Boondocks strips in question commented on the private life of the national security adviser and its relationship to her official duties in ways that violated our standards for taste, fairness and invasion of privacy."
The paper's ombudsman disagreed, arguing that: "The sequence of strips [was] within the bounds of allowable satire."
Shortly after 9/11, the New York Daily News pulled a short storyline about two new characters called Flaggee and Ribbon - a parody of the hyperpatriotism that swept the country at the time.
McGruder is nonchalant. "Papers pull the strip all the time. It's not really censorship because it's their paper. They can't tell me what to write and I can't tell them what to print."
Ironically it was 9/11 and the political climate that followed it that gave McGruder's voice both the edge and audience he was looking for. Deadlines for the strip had been making him ill with stress, and he worried about running out of ideas. "Then 9/11 happened and suddenly everything was different. They said irony was dead and humour was dead and there was nothing left to talk about."
Taking on the prevailing American mainstream, as well as the establishments of both the liberal left and black America, has made his strip popular, but it must make him lonely. With so few black and leftwing voices out there, how does he balance the demands of the under-represented constituencies of which he considers himself a part, and the demands of his cartoon? "You simply ignore any obligation you have to make everybody happy," he says. "And you focus on staying employed. I'm not saying that's a cop out to not be responsible. It's to say that everybody has a different understanding of what being responsible means. So you have to stay true to yourself. I have to ignore everyone and get my work done. That's not an excuse not to be responsible. It just means you can't let everyone tell you what you should be doing. Even if you're the only one doing it".
· Life in the Boondocks, presented by Gary Younge, will be broadcast on BBC Radio 4 at 10.30am on Saturday.