I did a quick Wikipedia check on first two of the mentioned organizations, CEI and the Heartland Institute. Both seem to acknowledge that the climate changes because of human action. They are called 'climate deniers' because the other side does not agree with them on policies.
Solely from Wikipedia. Given the extent of their policies denying the link between tobacco and health, between climate change and human activity (or it's a good thing really), I think you massively underplay why they attracted a label "denier".
On both tobacco and climate they are denying in the face of overwhelming evidence. Tobacco alone is enough for me to consider them entirely unethical and working against the public interest.
https://www.heartland.org/publications-resources/publication...
In this new volume, 117 scientists, economists, and other experts address and refute IPCC’s claim that the impacts of climate change on human well-being and the natural environment justify dramatic reductions in the use of fossil fuels
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