“Crud” is a word I was gifted by my midwestern upbringing. You have crud in the corners of your eyes when you wake up in the morning. You have crud in your skinned knee if you don’t clean and bandage it properly. Crud is the undesirable effluvia clogging up the functioning bits of your body and, it turns out, your thinking.
You cannot be properly described as “open-minded” if a gap in your knowledge is filled with crud, because that means that it’s exponentially more difficult to fill that gap with truth, with factual information, because the crud must be dislodged first.