During his long career as the most famous talk radio host in modern history, Rush Limbaugh has only rarely apologized for his rhetoric — so when he does, it’s worth pondering the contrition’s deeper meaning. Was his apology last week for calling a Georgetown University student a “slut” just a shrewd move to undercut a potential defamation lawsuit? Was it a frightened response to an intensifying backlash from advertisers? Does it prove the power of the liberal political organizations who have an ideological ax to grind against Limbaugh?

The answer to all those queries is yes — but none of those factors is the genuine news of the matter. Instead, what makes Limbaugh’s apology so important is its context. Capping off other similar brouhahas from across the mediasphere, Limbaugh’s mea culpa — however insincere — is significant because it is proof that America may be both setting some basic standards for political discourse and rejecting the right-wing shrieks about “censorship” and “political correctness.”

Consider what preceded Limbaugh’s apology. Only a few weeks ago, MSNBC announced it had terminated its relationship with Pat Buchanan, who had become a television mainstay despite the Anti-Defamation League documenting his long record as an “unrepentant bigot.” Just prior to that, Los Angeles radio station KFI suspended two hosts for calling Whitney Houston a “crack ho”; CNN suspended commentator Roland Martin for his homophobic Super Bowl tweets; and MSNBC suspended liberal host Ed Schultz for calling a competitor a “right-wing slut.” And before that, there was the seminal big-bang moment that kicked off the whole trend: the removal of Glenn Beck from Fox News — a decision that traced its roots to an advertiser boycott after Beck insisted that President Obama has a “deep-seated hatred of white people.”

In all of these examples, as with Limbaugh’s “slut” comment, the speech in question set off a firestorm not just because it was ideologically extreme, but also because it was indisputably inappropriate. To paraphrase the jurisprudential terms surrounding pornography, it crossed the line from merely offensive to overtly obscene.

Of course, this kind of slander was tolerated for decades without so much as a peep of objection from the media powers that be. Thanks to that silence, talk radio and cable television came to be wholly defined by such political obscenity — a development that made spectacularly lucrative careers for hate-speech demagogues.

That downward spiral seemed destined to continue because any time there was even a hint of protest, the conservative movement’s powerful media intimidation machine trotted out self-righteous rants against “political correctness” and odes to the First Amendment. Looking to manufacture its own insipid version of “political correctness” that crushes dissent, this machine typically portrayed conservatives as victims, marshaling anti-censorship arguments to insinuate that bigotry, anti-Semitism, homophobia and sexism are somehow entitled to a constitutionally protected place in major media outlets.

Not surprisingly, this same argument is now being made by conservatives in defense of their disgraced heroes.

“He has every right to his ideas, as we all have the right to our own,” wrote conservative Cal Thomas in an emblematic screed criticizing MSNBC for firing Buchanan. “It’s called free speech.”

It’s certainly true that all Americans have a right to their own ideas and to advocate for those opinions on their own. But having one’s ideas broadcast to millions of Americans over the public airwaves by major media corporations is not a right. It’s a privilege.

Limbaugh’s apology, made under pressure and designed to safeguard his privilege, concedes that indisputable truth. In doing so, the talk-radio icon is implicitly acknowledging a welcome change — one in which media executives, advertisers and the larger American audience are finally declaring that privileges can be withdrawn from those who violate the most basic standards of decorum.

David Sirota is a best-selling author of the new book “Back to Our Future: How the 1980s Explain the World We Live In Now.” He hosts the morning show on AM760 in Colorado. E-mail him at [email protected], follow him on Twitter @davidsirota or visit his website at www.davidsirota.com.