The phrase "look down upon" means to regard someone with contempt or disdain, often due to their perceived inferiority.

The opposite of this would be to regard someone positively or with affection, which is best expressed by "love" given in Option C. 

The other options—"abhor" (to detest), "be unsympathetic to" (to lack compassion), and "hate" (to strongly dislike)—all convey negative attitudes, which do not oppose the meaning of "look down upon."