The source of denialism may be rooted in species self hatred - or self destructive urges. Pick a weapon of mass destruction, and realize that so many destructive objects cannot be put in everybody's hands. Our very survival is based on restricting access to destructive power from all humans. Imagine every global citizen with a finger on an atomic weapon. Or every one with a bucket of toxins. How many will pull the trigger? Or kick the bucket?
So it is in the democracy of public opinion. in an age where an expressive, savvy individual can get at least 15 minutes of exposure... well anyone can become a pundit. That any few can strongly speak with a contrarian voice is expected. Ours is an age of Self Destruction by expression. That some use rhetoric, instead of atomic bombs, is just another dangerous method or device. Wielding and expressing species self contempt.