Except that it wasn't formal logic; the conclusion didn't follow from the premise, because there's nothing indicating that sickness is something which should be avoided. Therefore, the reader is expected to use information contextual to the world the author is in; namely, that sickness is bad, and should be avoided. Because there's also another possible world where -diseases- are good, and the construction wouldn't even make sense.
My roommate recently sent me a review article that LW might find interesting:
Personal observation says that LWers tend not to drink very much or often. Perhaps that should change, to the degree suggested by the article?
Full article here.