BOSTON >>Bill Cosby’s lawyers asked a federal judge on Friday to throw out a defamation lawsuit filed by three women accusing the comedian of decades-old sexual offenses.

The women, all of whom have stepped forward in recent years, say Cosby’s representatives publicly branded them as liars while trying to defend Cosby’s innocence.

But Cosby’s lawyers say the actor was merely acting in self-defense as his character was under attack.

“The law does not require that one stand idly by while he is publicly attacked,” the lawyers argue in their 38-page filing. “Instead the law entitles an individual who is accused of serious wrongdoing to rebut the allegations without facing defamation claims.”

The lawyers say Cosby denies all of the allegations of sexual misconduct.

Cosby, who famously starred as Dr. Cliff Huxtable on the beloved sitcom “The Cosby Show” from 1984 to 1992, hasn’t been charged with any crime. At least 15 women have stepped forward in recent years to level various assault accusations.

Tamara Green, a California lawyer, says Cosby drugged and sexually assaulted her in her Los Angeles-area apartment in the early 1970s.

Therese Serignese says Cosby drugged and raped her in a dressing room after a show in Las Vegas around 1976. And Linda Traitz alleges he tried to drug her and then groped her on a Southern California beach in about 1970.

Cosby’s lawyers say his representatives were responding to the accusations in strongly-worded rebukes.

One November 2014 statement references Traitz’s “extensive” criminal record, which includes larceny, fraud and drug possession charges.

“As the old saying goes, ‘consider the source,'” wrote Cosby attorney Martin Singer, who also attached copies of Traitz’s Florida criminal and prison records with the statement.

Another November 2014 statement cited by Cosby’s accusers offers “general comments” on the allegations and does not specifically name any of the accusers, his lawyers say.

“The new, never-before-heard claims from women who have come forward in the past two weeks with unsubstantiated, fantastical stories about things they say occurred 30, 40, or even 50 years ago have escalated far past the point of absurdity,” Singer wrote at the time. “It is long past time for this media vilification of Mr. Cosby to stop.”

The three women seek an unspecified amount of money for compensatory and punitive damages.

Many of the accusations against him exceed the statute of limitations for criminal prosecution. But the scandal has taken its toll on the 77-year-old actor and comedian as he has sought to revive his career with a national stand-up comedy tour.

Cosby has canceled or postponed more than a dozen performances as more accusers have come forward, and women’s groups have protested or threatened to rally at many of his public appearances.

Lawyers for the three accusers did not immediately respond to requests for comment Friday. They have until March 20 to file a reply to Cosby’s motion to dismiss the suit.

Green originally filed the defamation lawsuit in December 2014 and Serignese and Traitz joined later. The suit is filed in U.S. District Court in Springfield, in western Massachusetts. Cosby has a home nearby in Shelburne Falls.