Corollary to the Big Lie Theory

Once you get a group of True Believers sufficiently attached to a set of lies about critically important issues, then any person or institution trying to report the truth becomes discredited in their eyes.  If research, educational, journalistic, governmental groups, and NGOs become alarmed and continue to repeat the "discredited" claims, their protests only reinforce the certainty of True Believers that academic researchers, educators, etc. are lying scumbags.

This, in my opinion, is the main usefulness to the right of calling Global Warming a hoax -- it becomes a constant source of ridicule, generated by people who work enthusiastically for free, of the "MSM" (or Main Stream Media), the scientific community, etc.  The more alarmed and emotional they get about it, the more they get written off as "alarmists".  The parties responsible for the original deception can stand back and watch, without expending energy, or putting their fingerprints on the stream of abuse against their rival institutions.

While big oil like Exxon-Mobile have backed off from the memeplex they helped create (excepting the Kochs), right-coalition in general has become a huge beneficiary of this stream of abuse of sources frequently allied with liberals.  Hence they would have far too much to lose if they ever gave up their attacks on anything connected with Global Warming (esp. Al Gore, whom they would have to invent if he didn't exist).  Hence support for measures to mitigate climate change have become a third rail for Republican politicians -- grounds for organizations to place a well funded opponent in their next primary, while good soldiers who toe the party line, even if they lose, will get a nice sinecure at some think tank, if they need it.

There are some exceptions among the less automatically propagandistic elements of the right, like this National Review article.