When you say 'he' do you mean the black couple? How did they suffer? And why should the owner of the property they allege was for sale have to pay for his desire to not violate a convent, as repulsive as it may be to us?
"He" in the "archaic" English sense.
He suffered in not being permitted to come in consideration as a buyer. The owner was in absolutely no obligation to obey an illegal covenant, and in fact was in obligation to ignore it. (or as you put it "convent")
Assuming the accuracy of their side of the story, they were the initial victims enticed into stopping at his place by his "for sale" sign, only to be told that they could not buy because of the color of their skin. In my book, that is cause enough to afford them civil damages for their suffering (inconvenience).