It is difficult to get a man to understand something when his salary depends upon his not understanding it. -Upton Sinclair
Depressing though it may be, the above quote is consistent with many people's experiences in attempting to coax someone to a different opinion or just to convince someone to admit unlikable facts. If humans reached truth solely by accumulating and cross-checking knowledge obtained from trustworthy sources, as some philosophies presume, then the truth of a statement couldn't be so contingent on the effects of believing in the statement. Philosophical Pragmatism is singularly unsurprised, however. Since judgment is an ingredient in perception, biased judgment clouds perception. Seeing things "as they are", in practice means seeing things "as I see them". An isolated thing has no meaning. Brains compute meaning by laying isolated things side by side.
In the Pragmatist model, humans observe, reach conclusions, form plans based on those conclusions to reach goals, and then execute the plans. But this indivisible process can surely operate backward as well. Meaning, I don't want to act, therefore I doubt the conclusions that would force me to act, therefore I doubt the observations that would force those conclusions! The longer that a human clings to a "truth", the longer that a human selectively collects evidence in favor of it, and the stronger it becomes, by the human's design.
I'll end by noting a corollary of Sinclair's quote. It's difficult to get a politician to understand something when their election depends on their not understanding it. Basic accounting, biology, and climatology are notable examples.