I think it stems from the mistaken belief that a bad thing is merely lack of a good thing. Specifically, evil is merely a lack of good. Of course, this isn't correct at all, but it won't stop them from saying that. For the record, diseases are things in the sense that the bacteria/viruses that cause them are. Having typhoid isn't merely a lack of feeling good; you have to have something else in you (i.e. salmonella) in order to get the disease. It doesn't matter how many times nor how forcefully you knock down these arguments; someone will just prop them back up again as though nothing happened.

John Adams Wrote:The Government of the United States of America is not, in any sense, founded on the Christian religion.