“Reality has a left-wing bias,” our progressive friends love to tell conservatives. Then why are progressives so ruthless about distorting and covering up the truth?

As we learned from a bombshell Gizmodo report, liberal elites conspire to hide dissenting viewpoints from the public. Stories that appear in Facebook’s hugely influential “trending” box, one of the most important news sources in the world, are subjected to an ideological-correctness test.

Are Facebook users excited about the Conservative Political Action Conference? We can’t let that out. Are they upset about Lois Lerner? Bury it.

Black Lives Matter has been unmasked as an Astroturf movement that was given more prominence than it earned, while we now know that stories that come from RedState or other conservative outlets are placed in a Facebook info quarantine until they’re cleared by the good doctors of the Mainstream Media, i.e., the propaganda arm of progressivism.

Americans have long suspected the MSM isn’t playing it straight. “Reporters” who pose as nonideological beat writers — Dana Milbank of the Washington Post, Linda Greenhouse of the New York Times — later morph into fiercely opinionated columnists and are finally “revealed” to be hard-core leftists, as though we hadn’t guessed.

The internet seemed to offer a promising alternative. The gates to the printing presses were trampled down by the public. Now anyone could publish anything they chose, in front of the whole world.

But the world will never know what you have to say if the techno-elites ignore you. Google, Twitter and Facebook could (if they wanted to) offer pure objectivity by using a dispassionate algorithm based on nothing but traffic numbers. Instead, all three have given the public excellent cause to believe they’re doing the opposite.

Twitter hired a panel of liberal standards enforcers and began bouncing nonconformists, such as the outspoken right-wing blogger Robert Stacy McCain. Google has stated it’s considering whether to slant search results to give more prominence to what it “judges” to be true — which is exactly what progressive newspaper editors say they’re doing.

If Facebook is really an open community, it shouldn’t have news curators at all, just a program that genuinely reflects what people are talking about.

Why won’t they do that? Because shaping how the world thinks is too much fun to give it up.