Kevin Smith is recounting the time he told Harvey Weinstein to shut the fuck up. "I open the curtain at the back and I see Harvey outside, talking," recalls Smith. It was the premiere of his new movie Red State at the Sundance festival and Weinstein, his former boss and mentor, had promised to attend. But instead he was checking the American football scores. "He's talking about the Jets. Loud as fuck. The opening of my movie, first seven minutes. Old Kev just would have gone, 'Harvey, shh, movie's on.' But it disgusted me so much. It doesn't get much more heartbreaking. So I fuckin' lost it, and I went out and said, 'Hey. Shut the fuck up!' And he looked at me with fuckin' hate in his eyes. And I said, 'Yeah. That's me and I'm saying it.' And he just left."

Smith refers to "old Kev" and "new Kev" a lot. During the last few years he's "gone though hell and kept going", battling the film industry, critics, and himself. He's come out the other side reinvigorated, though, and with Red State he's made the best film of his career. The first time we speak, he's at his Hollywood Hills home, and over the course of a two-hour-plus phone conversation we get 10 interviews'-worth of monologues, diatribes and anecdotes, all as funny as they are frustrating as the Guardian tries to barge in with questions. There's a lot to discuss.

After the Weinsteins passed on the script, Smith set up a production company to make Red State, naming it The Harvey Boys in honour of the man who put him on the map. Smith's movie career, and his relationship with Weinstein, began in 1994 when Miramax (Weinstein's old company) bought Clerks, the slacker classic Smith made for $27,575 based on his experiences working in a convenience store. Smith was hailed as a new indie hero. He went on to make a series of well-received comedies set in his New Jersey "View Askewniverse" (Mallrats, Chasing Amy, Dogma, Jay And Silent Bob Strike Back) before 2004's ill-fated Jersey Girl raised eyebrows by casting Jennifer Lopez. He bounced back with 2006's Clerks 2, but a further knock was just around the corner in the shape of 2008's skewed romcom Zack And Miri Make A Porno, Smith's attempt to capitalise on the bawdy Judd Apatow comedies he saw himself as a part of. With Seth Rogen starring, it was expected to make around $30m on opening weekend; it did $10m.

"I felt so fucking terrible," says Smith. "I thought I'd ruined Seth's career; it was just depressing. It forced me into seclusion, I stayed offline and ended up smoking weed and watching a lot of hockey documentaries." Not in the mood to write, Smith agreed, for the first time, to direct someone else's screenplay, an action comedy called Cop Out. "I made it because I wanted to work with Bruce fuckin' Willis," he says now, "but more importantly I wanted to work inside the studio … before I ruled it out." He's proud of the film, but it wasn't a labour of love. The critics went to town on it.

'When I get a bad review, it's a bad review of me personally. They literally talk about my appearance and my clothing'

John Goodman in Red State.

"I pour a lot of myself into my movies," he says. "So when I get a bad review, that's a bad review of me personally. Motherfuckers literally talk about my appearance and my clothing." Despite his gripe with critics, Smith speaks freely about some of his films not being what they should have been; how his desire to tell stories was superseded by the desire to develop his career. "In the midst of Zack And Miri, something just felt kinda off. I'd hear myself going, 'Film used to be my passion, now it's my career.' The young Kevin Smith would fuckin' slap old Kevin Smith for saying that."

Old Kevin Smith hit rock bottom last year, with "the Southwest Airlines incident". On a flight from Oakland to Burbank, Southwest deemed Smith to be too fat for his seat and he was asked to leave the plane. Smith took to Twitter to air his grievances. The media then picked up the story and didn't take Smith's side. "I felt so fuckin' alone, dude," he says. "Jesus Christ! 5,000 articles, all of which say 'You're fat' in the headline." He felt the incident stripped him of his humanity to such an extent that it made him fearless, enabling him to "start an act two". "I know it was a funny story," he continues, "but to a fat guy with insecurities about his weight it was the worst thing that ever happened to me".

Smith wrote Red State in 2007 after watching his friend Malcolm Ingram's documentary Small Town Gay Bar. It featured an interview with Fred Phelps, leader of Kansas' Westboro Baptist Church, the folk who picket funerals and condemn homosexuals to hell. The Phelps footage was was "terrifying", says Smith. "He looks like a grandfather or your favourite uncle, and he speaks with 'Aw shucks' homespunisms, but the content of what he's talking about is pure fuckin' Hitler." Smith immediately saw the potential for a "quasi-horror" film and, newly shed of his inhibitions, was ready to make the kind of "grown-up" film he says he'd wanted to make all along. "I knew I couldn't do horror because I'm not Dario Argento, I'm not John Carpenter. But I felt like I could unnerve the audience."

After completing the script, Smith went back to his roots and offered it to the Weinsteins, who passed. Undeterred, Smith secured the $5m budget from two independent financiers, and announced that he would distribute it himself. He also declared he wouldn't spend money on marketing, and that he was going to retire from directing after his next film, Hit Somebody, a two-part opus about ice hockey.

'Film is not my first language. I'm a guy trying desperately to fit into an outfit that doesn't look good on him'

Michael Parks in Red State.

Smith says he's happy to distribute his own films, that after years of experience he knows who wants to watch his films and how to reach them. And sure enough, through foreign sales and Smith's film/Q&A roadshow, Red State has quickly recouped its costs. Ironically, though, the film he decided to market specifically to Kevin Smith fans is not at all what you'd expect from Kevin Smith; it's wildly unpredictable, scary, and funny in a way that none of his previous films have been. After the first UK screening at Brixton's Ritzy, Smith hit the stage to rapturous applause, speaking for an hour and a half about the film, about his gay brother's response, about how his dad died screaming, and about how he's abandoned his Twitter chats with the Westboro Baptist Church after one member suggested that Smith should run over his own daughter.

After the screening, we meet in the bar to ask Smith whether, in light of his renewed passion and the film's success, he's still planning to retire. He insists he is; he doesn't want to direct any more, it's too expensive and laborious, "a young person's game" (he's 41). Any further ideas will be executed via blogs, podcasts and comics. Besides, he says: "Film is not my first language. Here's a guy trying desperately to fit into an outfit that doesn't look good on him. You ever see me wear a suit? No, because I look stupid in adult clothing, so I dress like a fuckin' teenager all the time. People look at me in a suit and are like, 'Well technically he's dressed, but that's about it.' People look at my flicks and they go, 'Technically they're directed, but I don't know if they're directed very well.'"

On the strength of the incredibly effective Red State, they're wrong. For all Smith's claims to not care about critics any more, it seems they've certainly contributed to his decision to bow out of film-making. And that's a shame.