National Public Radio's decision to fire news analyst Juan Williams after he made controversial comments on Fox News about Muslims has become - for some Republican lawmakers, at least - a teachable moment. NPR, House speaker-in-waiting John Boehner (R-Ohio) said recently, is a "left-wing radio network" and should be stripped of federal funding. Eric Cantor, Mike Huckabee, Sarah Palin, Bill O'Reilly and other conservative voices have issued similar calls.

The Williams imbroglio is teachable, but its lessons actually point in the opposite direction: America's public media system, including NPR, requires more funding, not less. In particular, the funding should come from commercial broadcasters that profit from their licensed use of scarce public airwaves - and that would include News Corp., the parent of Fox News.

In this time of niche publications and cable networks that thrive on ideological anger, we should be seeking to strengthen NPR's role as a convener of the public square, a demagogue-free zone where all political and social groups - including conservatives and others opposed to federal funding of public media - should be welcome on equal terms.

During my six-year stint as managing editor of this newspaper, I made plenty of bad, time-pressured judgment calls. The Williams firing looks like a classic of the genre because it was carried out in a way guaranteed to obscure whatever merit the decision had. The precipitous speed with which NPR dispatched its most visible right-leaning voice and the defensive tone the network's leaders used to explain themselves made it entirely fair to question whether the network acted from ideological bias. Of course, Fox News displayed its own familiar, unabashed opportunism by quickly offering Williams a $2 million contract and pledging to protect his freedom of speech "on a daily basis."

The episode matters in part because NPR's place in American journalism and society is changing. Its growing audience of 30 million listeners - attracted by the network's worldwide reporting, lengthy interviews and deep analysis - increasingly constitutes a distinctive and influential commons, comparable to the audience served by the news divisions of major broadcast networks during the 1960s and 1970s.

Altogether, the public broadcasting system - NPR; its quasi-rival on radio, American Public Media; the Public Broadcasting Service on television; and the Corporation for Public Broadcasting, which provides them funding approved by Congress - reaches 98 percent of the American population. The system has achieved this penetration despite being comparatively starved of government-mandated investment. The United States spends about $1.40 per capita, or $420 million a year, on public and nonprofit media through the Corporation for Public Broadcasting. Britain spends about $87 per capita, according to an analysis by the advocacy and policy group Free Press. Canada, one of the most miserly industrialized democracies in this area, spends about $27 per capita.

NPR is the most effective nonprofit media organization in the country because of the excellence of its international and national reporting. Like all successful journalistic and cultural institutions, though, it must continually challenge its own complacency. ("Saturday Night Live," we can hope, will continue to keep NPR's producers honest; Alec Baldwin's hilarious "Schweddy Balls" skit suggests some of NPR's tendencies toward self-isolation.)

If it is open to criticism, the network can shed bad habits, innovate and diversify its programming by reaching out to member stations, audiences and outsiders.

When the British Broadcasting Corporation recently came under conservative criticism for allegedly tilting to the left, its managers conducted a review. They concluded that the BBC's reporting of particular stories was not typically biased against conservatives but that news subjects of concern to the right, such as immigration and business, were disproportionately neglected. A course correction broadened the BBC's audience and political support. NPR might benefit from a similar self-examination.

The network's self-critical evolution is vital because time, technological change and special interest lobbying have eroded to the vanishing point the public interest provisions of the 1934 Communications Act and other laws. Those provisions were intended to ensure that the commercial broadcasting industry helped strengthen the country's democracy by educating the public and promoting civil, inclusive debate. A modern, credible public media system anchored in NPR and PBS offers the best and most realistic way to address this failure.

To guide the broadcasting industry's public purpose, the Communications Act required that the nation's finite airwaves be allocated in "the public interest, convenience, and necessity." Today, for all the changes of the digital age, licensed broadcasters and other commercial media outlets still profit from exclusive access to public property - the airwaves, government-granted cable monopolies, satellite bands and the like.

Yet the bargain by which these businesses compensate the public for this access is broken and in urgent need of reform. Many journalists instinctively recoil from engaging the details of communications policy, fearing that it might invite government encroachment on press freedoms. But it would be no wiser to ignore this failure than it would be to stop regulating offshore oil leases or maintaining public parks.