When one asserts something that is false but that they honestly believe to be true, we don't accuse them of lying. Mistaken, uninformed, incorrect, undereducated and a number of other less charitable things that may insult their upbringing and intelligence, yes, but we don't impune their integrity by calling them a liar.
What about situations in which a person asserts something that is clearly and demonstrably false but genuinely believes it to be true even though they really should know better? Do we have a word for someone who deliberately ignores or avoids information that would cause them to concede their incorrectness?
This is the problem with young Earth creationists, abstinence only proponents, laissez-faire market advocates, many card players and all scriptural literalists. They're not liars; their intent is not to deceive but rather to spread ideas that they cannot comprehend as being false.
What is the word for that?