Will the world change if, as we may be told any moment, Rupert Murdoch is cleared to buy the whole of BSkyB? After all, he already controls the company as the dominant shareholder. So should we care if the government allows him to consolidate that control, especially if some arrangement is found to prevent him turning Sky News into Fox TV?

It matters because for Murdoch this is like stepping on an escalator that will move him steadily and without a pause to a position of far greater and broader control of our media. BSkyB will deliver him large amounts of cash year after year for the foreseeable future, and will enable him to outbid everybody for everything.

We know his domineering tendency from the world of sport. He has bought cricket and Premiership football, for example. No one can compete at auction with the prices he is prepared to pay, and the sports themselves can’t resist what he gives them. The result is no doubt good coverage where his executives choose to deliver it, but these sports are steadily ceasing to be public activities and instead becoming branches of his empire. His people decide on which days matches are played, and at what time they kick off. His employees have a great say in making stars and don’t care about bit-part players (look at the state of lower-division football). And fewer people see these sports because Sky is expensive — far, far more people saw the Ashes won on free-to-air terrestrial television in 2005 than on Sky in 2009.

But sport is just the start. Sky Atlantic shows us that Murdoch is also determined to monopolise big-budget television drama. He has bought (no one can compete) Mad Men, The Sopranos, Treme, Six Feet Under, Boardwalk Empire, Game of Thrones and many more. And he has also just bought Shine Group, the company behind Life on Mars, Spooks and Hustle.

The key to this growing dominance has been cash, and BSkyB will give him more and more of it. Murdoch talks about markets and want us to think he is out there competing, but competition is the last thing on his mind: he likes to own the market and in this country he is being allowed to buy it in big slices  in a way that amazes foreigners. Even more amazingly, people in government take seriously his complaints that the BBC is in his way, and are prepared to meddle with the corporation accordingly.

So he just buys everything, and if you want to watch it you have to pay, say, £45 a month to see it at the moment. The more he buys, the less there is elsewhere, the more you are obliged to watch Sky to see half-decent television and the more he can charge. And the BSkyB cash will help enormously.

Even if he was an ethical operator with an established record of transparent and fair dealing in public life we would be extremely foolish to allow him to step on that escalator. He is none of those things. He is a sinister and ruthless businessman with hard-right political views who treats British politics and public life with contempt. Go here and do what you can to stop him. And/or be ready to join a demonstration.

Brian Cathcart teaches journalism at Kingston University London. He Tweets at @BrianCathcart