Truthout is according to Wikipedia a "nonprofit, progressive news organization in the United States that operates a web site and distributes a daily newsletter". The Truthout website has published an article written by Richard Schiffman, who is described as " the author of two biographies as well as a journalist whose work has appeared in The New York Times, Salon, The Washington Post, The Christian Science Monitor, The Huffington Post, and on NPR and Monitor Radio."
In the article Schiffman, who maintains that "climate change is now virtually undisputed", joins the people who have condemned the Heartland Institute´s "offensive billboard campaign":
The science only gets better with time, and climate change is now virtually undisputed - by the people who are doing the science, at any rate. That it remains a "controversial issue" long after the results are in is thanks to a well-funded cabal of free-market think tanks, corporations and business groups that hope to win in the political arena a fight that they have long since lost in the halls of science. They are abetted by a media whose relish for conflict and a scientifically nonsensical sense of supposed "balance" has led them to give the deniers equal airtime.
In May, the Heartland Institute put up a billboard on the Eisenhower Expressway outside of Chicago comparing believers in climate change to the Unabomber, Ted Kaczynski. A firestorm in the press quickly convinced the Institute to pull the plug on the offensive billboard campaign.
However, Schiffman himself thinks that it is quite OK to compare "denialists" to Holocaust deniers: