A common refrain emerges during the “Superheroes” chapter of “Pioneers of Television,” the PBS documentary series returning this month that nostalgically looks at the medium’s past.

In almost every program — from “Wonder Woman” to “The Incredible Hulk” to “The Greatest American Hero” — performers talk about chafing against interference from “the network,” which invariably wanted to make the shows lighter, broader, more comedic.

This impulse to tone down material might have been maddening, even infantilizing, but it wasn’t wholly misguided, since back then kids still represented a major part of the networks’ primetime audience. And while it’s clear a more mature approach has resulted in better TV and movies — there’s no comparing the campy ’60s Adam West “Batman” played to Christian Bale’s “Dark Knight” — excising children from the equation is one of the least understood elements in the darkened nature of our media.

Kids haven’t been forgotten, of course, but rather sequestered — segregated onto their own brightly colored island, where they can safely pick from a bountiful menu of items like Pixar movies and Nickelodeon. Even disadvantaged kids have more options, as marketers eagerly slice the youth audience into tiny niches, from preschool to tweens.

Blocking access to baser media amounts to a giant technological game of Whac-a-Mole, but parents serious about governing their young kids’ media needn’t worry quite so much about children idly flipping on the TV looking for something to watch. In this personalized environment, it’s all waiting there for them, mediated by devices or services like DVRs and Netflix.

As for kids seeing inappropriate fare on broadcast TV, for all the media children under 12 devour, they’re simply no longer a significant component of the audience.

During the current season, a mere handful of primetime shows on the major networks average a 2 rating or better among kids, and they’re a pretty innocuous bunch: “Sunday Night Football,” “The Voice,” “Once Upon a Time,” “The Big Bang Theory” and “The Simpsons.” A decade ago, the number was six times that high.

Networks are more than happy to ignore tykes because — like most of their grandparents — they can’t sell them to advertisers. The watershed moment came in the 1990s, when Fox began scheduling edgier fare earlier in the evening, and NBC moved “Mad About You” and subsequently “Friends” into the 8 p.m. slot.

The so-called “Family Hour” had always been an ephemeral notion — advanced mostly by cultural scolds — but as TV exec Garth Ancier said at the time, “When Fox started moving shows that did well with adults (to 8 p.m.), it was like a dam was broken, and everybody started programming differently.”

Removing kids from the conversation, however, leaves those fretful about the relationship between media and society with at best a wobbly leg to stand on. Politically speaking, protecting children has always been a winner — the kind of argument it’s difficult to rebut.

Seeking to curb what adults choose to watch is more problematic. Granted, some might think Fox’s new serial-killer drama “The Following” pushes too far into the realm of grim and icky, or find CBS’ “2 Broke Girls” too raunchy, but others won’t. Beyond speculating about what might potentially inspire disturbed minds, such a debate is purely subjective.

Concerns pertaining to children represented the system’s one reliable brake to restrain entertainment standards, for good and ill. With that responsibility diminished (if not, perhaps, wholly removed), the foundation for policing content begins to crumble. Sure, slap on ratings or advisories to assist parents, try shaming those who deserve it, but after that it’s let the marketplace decide and the media buyer beware.

Some critics won’t easily relinquish the gauzy ideal of a collective hearth where families gather around the TV together — an image as dated as a clunky old cathode-ray-tube set.

Even so, shifting technology and exploding choices have conspired to undercut “Save the children” as a battle cry for those alarmed by a perceived coarsening of the media environment.

That’s not to say such considerations lack merit or don’t warrant discussion. Still, for those who see the steady drip toward greater creative license as a tide of raw sewage, invoking the kids won’t turn back the clock to TV’s pioneer days.