My problem with said person wasn't that he didn't understand the technical meaning of "dpi" (not understanding it is perfectly forgivable to a nontechnical pers

My problem with said person wasn't that he didn't understand the technical meaning of "dpi" (not understanding it is perfectly forgivable to a nontechnical person), but that he flat out refused to follow my attempt of explaining that it is simply number of pixels divided by number of inches. Now, if that person was unknown to me, I would assume that he is being rude, but in this case I knew him well enough to conclude that his wilful ignorance was due to "fear of math" (he never learned basic fractions in school, and moreover he had a big enough ego to consider such knowledge unnecessary, which put him in a state of denial).