So I’m watching Sacha Baron Cohen in his box office-conquering “Bruno” and laughing. And, between laughs, I say to myself, “Well, that’s probably it. Mainstream American homophobia has now been quite effectively marginalized at the movies, the way mainstream American racism was decades earlier.”

You had to have a “Blazing Saddles” before you had a Barack Obama. And “Bruno,” as much as anything I’ve ever seen, laughs the older and more traditional forms of sexual prejudice right off the screen. (Bruno, it’s key to understand, isn’t actually gay; he’s a burlesque of a frightened homophobe’s worst nightmare of gayness.)

The old mainstream homophobia is on its last legs, and it seems to me it’s dying quickly, rather than slowly.

I’m not saying “Bruno” caused the sea change —or even “Brokeback Mountain” before it— only that in its envelope-pushing way, it marked that sea change.

Where did it actually come from? Television, the great American social normative. And where in television? Two places, I think —sitcoms and afternoon television.

The existence of sitcoms as a gay power enclave has been publicly noted for decades, but the first major annunciation came in 1996 when gay critic David Ehrenstein wrote a landmark piece in Los Angeles magazine that was blurbed thus on its cover: “How Sitcoms Became the New Gay Art Form.” Wrote Ehrenstein, “Since current comedies are positively obsessed with the intimate sex lives of straight young singles, who better to write them than members of a minority famed for its sexual candor?”

When I wrote a TV Topics column about Ehrenstein’s piece, a local late-night talkmeister (who is no longer with us) turned it into a whole paranoid handwringing broadcast. He seemed to think taking note of Ehrenstein’s milestone piece and the obvious facts it presented was a combination of advocacy and confession. He seemed to believe he’d thrown open my closet with a loud “a-ha!” and exposed a crusade against “family values,” not realizing that it was the very idea of “family values” that was being reconfigured everywhere you looked on the tube.

Boy, did he ever have the wrong closet, but that show was a classic example of the kind of semi-Gothic haranguing on the subject that “Bruno” is now helping to laugh into well-deserved oblivion.

Ehrenstein later went on to write “Open Secret: Gay Hollywood 1928-2000” and to say wittily in a New York Times interview that things have changed so much that the way young gays now “come out” to their parents is to say, “I want to write a sitcom.”

Even more important than sitcoms as a launching pad for sexual tolerance, though, was afternoon television, whose predominantly female audience has been feasting on an open investigation of previously hidden life for 40 years.

Oprah Winfrey, of course, is its center—an ongoing sociopolitical influence singular in our history.

But I remember where Winfrey came from— Phil Donahue, who got his TV start 13 years before Oprah and was the first to realize that the women watching him in the afternoon wanted a lot more from daytime TV than apple pie and showbiz vapidity, Mike Douglas style.

In his relentlessly exploitive exploration of “alternative lifestyles,” Donahue merrily uncovered for his curious daytime audiences the stuff of other people’s midnight fears. You can’t launder all that minority life in public and leave it openly out in the sun to dry without the neighborhood getting awfully used to seeing what were once “unmentionables”— and realizing “hey, it’s just laundry.”

It is, I think, Phil Donahue’s America in the 21st century.

The truly remarkable part of the Donahue story is that while he wound up marrying Danny Thomas’ sitcom star daughter Marlo, Donahue got his TV start not on the wicked American coasts where, as we all know, Sodom and Gomorrah reside, but in Dayton, Ohio, the very heart of the heart of the country.

The other irony, of course, is that once Donahue decisively steered the ship of daytime TV in an entirely different and more sensational direction from where it had always gone, his work was done. His increasingly political concerns have continually scotched efforts to revive his career.

It’s his—and Mel Brooks’—America, then, where “Bruno” can lead the box office pack on a slow July weekend, but it’s an America where Donahue himself can’t find a place anymore.

But then Phil Donahue will be 74 on his next birthday in December. Undoubtedly, there are some who’d say he’s already done quite enough.