Using the definition of "disease", it actually fits.
Many people assume "disease" means an acute illness, and many others think it as an emotive term, i.e., "I'm not diseased! I'm perfect!"
So yeah, the statement down the bottom of the page is factually wrong.
To add:
Quote:
1. A pathological condition of a part, organ, or system of an organism resulting from various causes, such as infection, genetic defect, or environmental stress, and characterized by an identifiable group of signs or symptoms.
2. A condition or tendency, as of society, regarded as abnormal and harmful.
3. Obsolete Lack of ease; trouble.