Political scientist Brendan Nyhan, who has made a study of this, despairs that is almost impossible to correct misinformation.
This is partly because we all filter information through the lens of our deep-seated beliefs. When presented with news that challenges what we believe, it's easier to doubt its accuracy than to change what we have long held true.
Furthermore, once information is captured in our memory, it's very difficult to undo its emotional effect. And the more often we hear misinformation, its very familiarity makes it seem even more true.
So the more often a lie is corrected, the more it becomes familiar, and the more familiar it is, the more true it seems. As a result, corrections can have the perverse effect of reconfirming misinformation.
But Nyhan has come up with a last-stand strategy. He told PBS's Brooke Gladstone that he thinks the only real solution is "to shame the people who are promoting these things, who are putting them out there."
"At some point, people have to be cast out of polite society," Nyhan said. "You have to simply say, that is irresponsible and we're not going to give you our air time, our print to make that sort of a claim."
To Nyhan, it's kind of a free-market solution. "Politicians and talk radio hosts, they're going to push these things when it’s in their interest to do so," he said. "It’s a simple cost-benefit calculation. What I want to do is increase the cost."
The cost of Rush Limbaugh's thoughtless and tasteless ranting increased last week when he slandered a Georgetown University law student who argued that all insurance plans should cover birth control.
He finally went so far over the line that advertisers were embarrassed to be associated with him. The CEO of Carbonite, for example, said, “We hope that our action, along with the other advertisers who have already withdrawn their ads, will ultimately contribute to a more civilized public discourse.”
Let's be clear, this is not the same as trying to get someone fired because of who she is, as happened when the religious right protested JC Penney's hiring of Ellen DeGeneres. It's refusing to be associated with someone who consistently poisons the well in the center of the public square.
And let's be honest, for every Rush Limbaugh, there's a Michael Moore.