The word "denialist" refers to someone who refuses to accept or acknowledge certain facts or evidence, usually related to a controversial topic. Full definition
I think people are being far too kind to climate change denialists by assuming they're arguing in good faith. (blogs.discovermagazine.com)
There is a good article on the PR methods used by denialists in Eur J Public Health vol 19 pp 2 - 4. (realclimate.org)
Here's a section in which he asserts that many climate campaigners and climate scientists are overly concerned about the impact of denialists on public attitudes: (dotearth.blogs.nytimes.com)