Skeptic

Also: Denier, Denial, Denialist, Contrarian, Sceptic, Skepticism, Scepticism

Definition used in the MOOC Denial101x:

Genuine scientific skepticism is a good thing. In fact, it’s the heart of the scientific method. Genuine skeptics don’t come to a conclusion until they have considered the evidence. In contrast, people who deny well-established science come to a conclusion first, and then discount any evidence that conflicts with their beliefs. That means that denial and skepticism are polar opposites.