One of the most troubling examples of what I believe is self deception is the story of Linus Pauling. He was a brilliant scientist. He is the only person who has ever won a scientific Nobel prize and the Nobel peace prize and the only person to received two unshared Nobel prizes. He is the founder of Quantum Chemistry and has had an indelible affect on science. He spanned the disciplines of inorganic chemistry and organic chemistry.
Then he seemed to descend into a whirlwind of self deception, first with mega doses of Vitamin C for the common cold then to suggest that it could cure cancer. There is no evidence of these claims and he continued to deny the results of subsequent research that showed that Vitamin C was not better than a placebo for the common cold and his beliefs about Vitamin C and cancer border on quackery. It seems like it would take an extraordinary level of self deception to hold his beliefs about vitamins against overwhelming evidence.