Why Rizal compared Noli Me Tangere to a social cancer?

Rizal compared Noli me Tangere to a cancer in order to open the eyes of his countrymen to their true condition, and expose the spreading sickness of the Spaniards, all while making them aware of the errors and injustices committed in their name.

“In the catalogue of human ills there is to be found a cancer so malignant that the least touch inflames and causes agonizing pains; afflicted with such a cancer, a social cancer, has your dear image appeared to me, when, for my own heart’s ease or to compare you with others, I have sought, in the centers of modern civilization, to call you to mind.

“Now, desirous of your welfare, which is also ours, and seeking the best cure for your ills, I shall do with you what was done in ages past with the sick, who were exposed on the steps of the temple so that the worshippers, having invoked the god, should each propose a remedy.

“To this end, I shall endeavor to show your condition, faithfully and ruthlessly, I shall lift a corner of the veil which shrouds the disease sacrificing to the truth everything even self-love – for, as your son, your defects and weaknesses are also mine.”