In what way does the author think Jesus challenged society by touching the leper?

The author draws a distinction between disease, which he defines as an individual experience, and illness which he claims is the stigma associated with having the disease. This suggests that in touching the leper Jesus was in fact curing the illness by transcending stigma. This is another illustration of how Jesus actively challenged prevailing thought and belief and, in this particular case, metaphorically took the leper into the Kingdom of God.