Because they believe this, does not mean that it is correct. Often times these people do have quite a lot of knowledge and the having of knowledge leads them to believe that they know more than they do. Because they know and understand the tangible, they think that they are qualified to know that the intangible is rubbish. If the person is not aware of their spirituality, they may believe they are right in calling all spiritual things hocus pocus, gibberish or gobbledygook.
Some people go so far as to call anything spiritual, evil.
I personally know of people who believe that astrology and astrologers are evil. Some people say that you will die if you do not eat for 25 days. Yes, these people probably would die, partly because they believe they will. What a silly question someone might think. Of course it is the inside.