Many liberals and progressives fear that Sinclair Broadcast Group’s attempt to buy Tribune Media will result in a new, all-powerful, Trump-aligned national TV network and deepen the conservative movement’s existing dominance of radio. To be sure, Sinclair’s existing programming is to the right of Fox News.

'The most dangerous US company you have never heard of": Sinclair, a rightwing media giant Read more

But this is not the right reason to challenge the deal. Neither liberals nor conservatives should allow the government to approve or disapprove of media mergers based on the corporation’s political ideology. The right reason to oppose this deal is that Sinclair’s size and market dominance already threatens the open marketplace of ideas upon which our democracy depends. Allowing Sinclair to combine with another media giant would only make the threat worse.

Sinclair is so large that it would have been illegal throughout most of the 20th century. Into the 1980s, the Federal Communication Commission (FCC) enforced strict limits on the number of broadcast stations that one company could own. The so-called “rule of seven” blocked any company from owning more than seven AM, seven FM, and seven TV stations.

But in 1984, a Republican-led FCC significantly raised those limits, replacing the “rule of seven” with a “rule of 12” that allowed companies to own nearly twice as many stations. A decade later, Democrats and Republicans in Congress united with Bill Clinton to replace those limits with a “national ownership cap” that allowed a single company to own TV stations reaching up to 35% of American households.

A diverse, de-concentrated, and competitive media system protects free speech in the United States

The vote totals for the 1996 law reveal how deeply both parties were implicated in this retreat from traditional anti-monopoly protections in news media:s 414 House members and 91 senators voted for the law. Clinton said the new license to consolidate would promote “competition as the key to opening new markets and new opportunities”.

That was not what happened. Instead, as many critics predicted, big corporations rolled up control across media market after media market. And the process continues. When the Bush-era FCC proposed raising the cap to 45% in 2003, Congress split the difference, setting the national ownership cap at 39%, where it stands today. Sinclair currently reaches around 38% of American households.

In April, FCC chairman Ajit Pai – relying on an outdated loophole from the days of UHF broadcast stations – cleared the way for media corporations to essentially buy up as many local stations as they want, wherever they want. A few weeks later, Sinclair announced its plan to buy Tribune. If approved, the deal would give Sinclair access to 72% of American households.

The Telecommunications Act of 1996 did not just permit consolidation in TV. It paved the way for radio monopolization as well. Before the law, it was illegal for one company to own more than 40 radio stations. Today, the company formerly known as Clear Channel – iHeartMedia – owns 858 stations.

The rise of the media conglomerate Comcast follows a similar story. For decades, it was illegal for networks like NBC and other big players to control companies in multiple forms of media, like film and TV. But the 1996 telecoms law and other changes got rid of many of those limits. In 2011, Comcast relied on these changes when making the case that it should be free to buy NBC, in a deal that broke decades of precedent against vertical integration. Today, the combined corporations own properties active in TV, film, cable and broadband internet. AT&T’s bid to acquire Time Warner would produce a similar sort of conglomerate.

AT&T's Time Warner takeover: justice department aims to block $85bn deal Read more

These levels of consolidation are a threat to democracy regardless of whether liberal or conservative messages dominate. In 1947, the Hutchins Commission, a group of academics convened to study the freedom of the press, put it this way: “The owners and managers of the press determine which persons, which facts, which versions of the facts, and which ideas shall reach the public.”

A diverse, de-concentrated, and competitive media system protects free speech in the United States. It guarantees that public discourse cannot be monopolized by concentrated power, whether in form of populist demagogues or corporate plutocrats, as it is in so many less fortunate nations.

On Monday, the justice department moved to block AT&T’s plan to buy Time Warner. That same day, a trio of senior House Democrats – Nancy Pelosi, Frank Pallone and Mike Doyle – demanded that the FCC bar Sinclair’s purchase of Tribune Media unless Sinclair sells off several TV stations.

Both actions are important steps in the right direction, but neither goes far enough. It is time for members of Congress from both parties to return to their traditional approach to news and entertainment, and take the steps necessary to block all concentrations of power that threaten diversity of ownership over the news, not only at the national level but also in every city and town across America.