DENIS Leary, already under attack for making fun of autism, is now defending his right to call homosexual men “fags.” And incredibly, he says the Catholic Church and his parents are to blame for his slurs.

The “Rescue Me” star is put on the defensive in an interview with next month’s issue of gay magazine The Advocate, which grilled him about his upcoming book, “Why We Suck,” and a chapter titled “Matt Dillon Is a Giant Fag.”

“What gives you the right to use the ‘F-word?’ ” demands interviewer Brandon Voss. “I also have a chapter called, ‘We’d Hate You Even If You Weren’t Black,’ ” Leary shoots back. “I don’t believe in the power of words. My parents came from Ireland, where the [C-word] is literally a word your mother and father would use to describe the weather or the car: ‘That [C-word]ing car won’t start!’ And I come from a Catholic background where the nuns were always telling you, ‘Don’t do this, don’t say this,’ so any time anyone tells me I shouldn’t say something, my reaction is, ‘Why not?’ ”

The Advocate also takes Leary to task over a 2006 Elle interview where he was asked to name a man he’d sleep with if his life depended on it. “I’d shoot myself in the head,” Leary answered. He tells Voss, “I’d have to have my wife dress up as a man. I never met him, but I always really loved Paul Newman – not only as an actor, but also the way he carried himself . . . So I guess I’d have to dress my wife up as Paul Newman.”

Leary came under fire last week after Page Six revealed how his book says many kids diagnosed with autism are “just stupid. Or lazy. Or both.” It infuriated parents and sparked a new Web site, denislearysucks.com.

The Boston Globe reported dozens of alumni from Emerson College, which Leary attended, are incensed the school continues to use him as a fund-raiser. Leary has insisted his remarks were taken out of context.