When it comes to media, bigger is not better. And when it comes to the control of the infrastructure of how we communicate now, the trend toward extreme bigness—as illustrated by Comcast’s plan to buy Time Warner Cable and create an unprecedented cable combine—is accelerating at a dangerous pace.

In the aftermath of a federal court decision striking down net neutrality protections that were developed to maintain an open and freewheeling discourse on the Internet, and with journalism threatened at every turn by cuts and closures, the idea of merging Comcast and Time Warner poses a threat that ought to be met with official scrutiny and grassroots opposition.

The point of the free-press protection that is outlined in the First Amendment is not to free billionaire media moguls and speculators to make more money. The point is to have a variety of voices, with multiple entry points for multiple points of view and a communications infrastructure that fosters debate, dissent and democratic discourse.

When media conglomerates merge, they do not provide better service or better democracy. They create the sort of monopolies and duopolies that constrain America’s promise. Franklin Delano Roosevelt was right when he decried “concentration of economic power in the few” and warned that “that business monopoly in America paralyzes the system of free enterprise on which it is grafted, and is as fatal to those who manipulate it as to the people who suffer beneath its impositions.”

Merging the two largest cable providers is a big deal in and of itself—allowing one company to become a definitional player in major media markets across the country—but this goes far beyond cable. By expanding its dominance of video and Internet communications into what the Los Angeles Times describes as a “juggernaut” with 30 million subscribers, the company that already controls Universal Studios can drive hard bargains with content providers. It can also define the scope and character of news and public-service programming in dozens of states and hundreds of major cities—including Chicago, Los Angeles, Philadelphia, New York City and Washington, DC.

That’s too much power for any one corporation to have, especially a corporation that has been on a buying spree. Comcast already controls NBCUniversal and a broadcast and cable empire that includes NBC, CNBC, MSNBC, the USA Network, Telemundo and various other networks.

It’s bad for consumers.

“In an already uncompetitive market with high prices that keep going up and up, a merger of the two biggest cable companies should be unthinkable. The deal would be a disaster for consumers and must be stopped,” says Craig Aaron, the president of the media-reform group Free Press.

It’s bad for musicians, documentary makers and other creators.

“Comcast’s proposed takeover of Time Warner would give one company incredible influence over how music and other media is accessed and under what conditions,” says Casey Rae, interim executive director of the Future of Music Coalition, who noted “the ever present danger of a huge corporation like Comcast—which already owns a major content company—disadvantaging competition or locking creators into unfair economic structures.”

And it is bad for the democratic discourse of a nation founded on the premise memorably expressed by Thomas Jefferson in 1804 when he wrote, “No experiment can be more interesting than that we are now trying, and which we trust will end in establishing the fact, that man may be governed by reason and truth. Our first object should therefore be, to leave open to him all the avenues to truth. The most effectual hitherto found, is the freedom of the press.”

The idea that “all the avenues to truth” would be controlled by a monopoly, a duopoly or any small circle of multinational communications conglomerates is antithetical to the understanding of the authors of a free press, and of its true defenders across the centuries.

So yes, US Senator Al Franken—the Minnesota Democrat who has proven to be one of the most serious and savvy congressional watchdogs on communication policy—is absolutely right when he says, “There’s not enough competition in this space; we need more competition. This is going in the wrong direction.”

Franken has written to the US Department of Justice, the Federal Trade Commission and the Federal Communications Commission, urging each of them “to act quickly and decisively to ensure that consumers are not exposed to increased cable prices and decreased quality of service as a result of this transaction.”

The FCC, in particular, has broad authority to review telecommunications-industry mergers, with an eye toward determining whether they are in the public interest. And watchdog groups have been pressuring the commission’s new chairman, Tom Wheeler, to assert the FCC’s authority. For Wheeler, a former president of the National Cable and Telecommunications Association, the lobbying organization for the cable industry, this is will be a critical test of his leadership.

But challenges to this proposed merger must also come from the anti-trust lawyers at the Department of Justice and the congressional watchdogs over consolidation and monopoly issues.

“Stopping this kind of deal is exactly why we have antitrust laws,” says Free Press’s Aaron.

The congressional role cannot be underestimated. The Department of Justice, the FTC and the FCC get cues from Congress. And the voices of members of the House and Senate will play a critical role in determining whether the merger goes forward.

Some of the initial signals have been good.

“This proposed merger could have a significant impact on the cable industry and affect consumers across the country,” says Minnesota Democrat Amy Klobuchar, the chair of the Senate Antitrust Subcommittee, who announced: “I plan to hold a hearing to carefully scrutinize the details of this merger and its potential consequences for both consumers and competition.”

The ranking Republican on the committee, Utah Senator Mike Lee, supports the review, as do public interest groups ranging from Public Knowledge to Consumers Union.

But hearings will not be enough. The Senate, in particular, must send clear signals.

Former FCC Commissioner Mike Copps is precisely right when he says of the idea of creating an even larger telecommunications conglomerate, “This is so over the top that it ought to be dead on arrival at the FCC.”

Copps, who now serves as a special adviser to Common Cause’s Media and Democracy Reform Initiative, is also right when he says, “The proposed deal runs roughshod over competition and consumer choice and is an affront to the public interest.”

But the public interest will prevail only if the public, and its elected representatives, raise an outcry in defense of the robust competition that opens “all the avenues to truth.”

John Nichols is a co-founder, with Robert W. McChesney, of Free Press. Nichols and McChesney are the authors of the book The Death and Life of American Journalism: The Media Revolution that Will Begin the World Again (Nation Books).

Take Action: Stop the Comcast/Time Warner Cable Merger