There are a lot more possible explanations. For example another one is that some groups are pushing skepticism of science and scientists as a political tactic. Libertarians groups seem to fund an aweful lot of anti-science campaigns, for example. That may be because scientific evidence is often used to restrain the activities that free enterprise can engage in, something many libertarians oppose. They know attacking the messenger can prevent the message from being heard. In particular, in the climate change area, acceptance that there is a broad consensus of opinion among scientists and that the consensus supports global warming overwhelming tends to substantially increase acceptance of the findings. Thus, attacking the science and the consensus could be seen as a pre-emptive strike to prevent regulation and the dreaded source of all evil - government, for libertarians. I'm sure you could name other groups who have similar reasons to oppose the consequences of accepting certain streams of science.