People refuse to believe that which they dont want to believe, in spite of evidence. When explorers first went to Australia they found a mammal which laid eggs; spent some time in water, some on land; had a broad, flat tail, webbed feet, and a bill similar to a duck.
Upon their return to England, they told the populace of this, and all felt it was a hoax. They returned to Australia and found a pelt from this animal and took it back to England, but the people still felt it was a hoax. In spite of the evidence, they disbelieved because they didnt want to believe.