News and opinion parted company fairly late in the history of journalism, a split usually dated to the mid-19th century advent of steam-powered presses, paper mass-produced from wood pulp and a revenue model based on consumer advertising.

Together, those developments meant size mattered. And big circulation was easier to achieve if news was presented without ideological topspin, so that people of different beliefs could read the same accounts without having their feathers ruffled.

Until then, political alignment had been a driver of newspaper journalism, and it has remained integral to magazines, documentaries and other media. But for the burgeoning metro press, opinion came to be deplored as an impurity, an ideological contaminant — and the language of ethics was thus hitched to the wagon of commercial calculation, not for the last time.

Still, keeping opinion from sullying fact is a duty U.S. journalists take seriously, to a degree that civilians find surprising. Reporters are trained in a discipline that encourages them to present current realities in ways that keep their own opinions out of sight and, they hope, out of the reader’s mind.

True, there’s a bogus element to this. Stories can’t be told, or even conceived, without judgments about what matters, and those judgments reflect the values of individuals and of the institutions they operate in. So even if, in the traditional paper, the newsroom chief and the opinions editor didn’t compare notes, they did breathe the same air and, ultimately, were held to the standards of the same bosses and owners.

Still, the success of a news organization depended in part on its reputation for independence — from the town fathers, from its advertisers, even from its owners.

That brings us to the media ownership issue of the moment: the possibility that Charles and David Koch, reputedly the country’s most open-handed funders of libertarian causes, will buy all or part of the Tribune Co. Along with 23 broadcast and online properties, Tribune has eight regional newspapers, including the Los Angeles Times (the country’s fourth-biggest paper), Chicago Tribune, Baltimore Sun, Orlando Sentinel, South Florida Sun-Sentinel, Hartford Courant and Hoy, the No. 2 U.S. Spanish-language sheet.

The brothers are estimated to be worth $34 billion each, making them the fifth- and sixth-richest men on Earth. Their privately held Koch Industries is primarily in energy and chemicals, and its holdings range from pipelines to manufacture.

The Kochs are intensely active in the public sphere as warriors for the libertarian cause, having endowed university chairs for free marketeers, given generously to the Cato Institute, the prestigious rightist think tank and bankrolled Americans for Prosperity, which helped create tea party-related groups. They also contributed to the campaign in Wisconsin against government employee trade unions.

No entrants into media ownership ranks would be more dreaded and reviled by liberals, and activists have begun mobilizing to stop Tribune Co.’s owners — notably, funds that manage pension funds for trade unions — from selling to the brothers.

The assumption, which seems right, is that the only reason the brothers would pay $600-plus million for a newspaper company that’s just recently emerged from bankruptcy is because they want influence. At a Koch-sponsored conference of like-minded rich in Aspen, Colo., in 2010, The New York Times reported, the brothers unveiled “a three-pronged, 10-year strategy to shift the country toward a smaller government with less regulation and taxes.” Key to that strategy was media control.

OK, so what? Media proprietors have long imagined themselves philosopher-kings, from Greeley to Pulitzer and Hearst, from McCormick to the Knight brothers, the Chandlers, Grahams, Sulzbergers and Murdochs. After all, why own a newspaper if all you care about is profits (good luck with that) — if you don’t care what it’s used for?

And good luck with that, too. The reality, the brothers may find, is that a quality news organization is a rambunctious, highly strung and poorly restrained pack of skilled, dedicated malcontents who, like well-bred retrievers, will persist in bringing back choice game, even when it isn’t the quarry the hunter was after.

Sure, the Kochs could try to subjugate their newsrooms and force upon them a political line: Confine them to ideologically correct stories that discredit government programs, squelch investigations into corporate regulation, focus on union corruption, trash environmental oversight, ignore boardroom self-dealing.

But in no time, their papers would be known for narrowly targeted hatchet jobs, and their stories would get meager pickup from other media and scant attention from the wider public. The influence the brothers were seeking would recede from their grasp.

They might very well find that if they want to succeed as publishers, they needed to start acting like publishers.