Very good article!

A couple of comments:

So here, at last, is a rule for which diseases we offer sympathy, and which we offer condemnation: if giving condemnation instead of sympathy decreases the incidence of the disease enough to be worth the hurt feelings, condemn; otherwise, sympathize.

Almost agreed: It is also important to recheck criterion 4:

Something unpleasant; when you have it, you want to get rid of it

to see if reducing the incidence of the disease is actually a worthwhile goal.

On another note:

Cancer satisfies every one of these criteria, and so we have no qualms whatsoever >about classifying it as a disease.

Criterion 3:

Something rare; the vast majority of people don't have it

is somewhat arguable, at least for some types. Quoth Wikipedia

Autopsy studies of Chinese, German, Israeli, Jamaican, Swedish, and Ugandan men who died of other causes have found prostate cancer in thirty percent of men in their 50s, and in eighty percent of men in their 70s