Some of the biggest (richest) global-climate-change deniers also happen to be the biggest contributors to greenhouse gases -- the oil, coal, and automobile industries. We now know that these industries were being told by their own scientists that "the scientific basis for the Greenhouse Effect and the potential impact of human emissions of greenhouse gases such as CO2 on climate is well established and cannot be denied."
The oil, coal, and automobile industries did not just ignore what their own scientists were saying. They lied about it. Through an industry-funded "front" calling itself the Global Climate Coalition, the Dirty Air People conducted a multimillion-dollar advertising campaign challenging the scientific merits of climate change, greenhouse gases, and their own culpability in exacerbating the problems. Among the hungry fish who swallowed that bait were umpteen conservative "pundits."
"By questioning the science on global warming ... groups like the Global Climate Coalition were able to sow enough doubt to blunt public concern about a consequential issue and delay government action."
The handmaidens to this policy of "confuse the issue and delay reform" were the news media, particularly TV news and especially cable news, where supposedly "neutral coverage" demands the 50-50 approach. If you have two scientists saying global warming cannot be denied, then you must put on two "scientists" saying it's all a crock.