Finally an explanation:
"In the psychology of human behavior, denialism is a person's choice to den y reality, as a way to avoid a psychologically uncomfortable truth."
"The terms Holocaust denialism and AIDS denialism describe the denial of th e facts and the reality of the subject matters,[4] and the term climate cha nge denialist is applied to people who argue against the scientific consens us that the global warming of planet Earth is a real and occurring event pr imarily caused by human activity."