Denialism: Countering With Evidence
Denialism is the radical, controversial rejection of basic, socially accepted and empirically verified concepts supported by overwhelming evidence. Denialism is an attitude about social, political, or scientific issues. It is differentiated from denial, the defense mechanism that protects the personality by keeping unacceptable thoughts, wishes, or emotions from conscious awareness.
Reasonable, legitimate dialogue with a denialist is difficult. You will be interrupted often as he overreacts to defend his bigoted, bizarre, or unreasonable ideas against scientific facts. You may be rudely overridden, intentionally sidetracked, or loudly distracted from the orderly flow of discussion. In a large public gathering, your rights of expression and of free assembly may be suppressed.
Be ready to calmly support your argument with hard data, and to cite your specific research sources.