Odysseus describes the Cyclops as a "horrid creature, not like a human being at all," with a "loud voice and monstrous form." Polyphemus lives in a dirty cave, where he tends to his goats and sheep, a lifestyle that Odysseus and his warriors view as barbaric. Odysseus, a king of the civilized Mycenaeans, is disdainful of the lawless lifestyle of the Cyclops, which is symbolized by his inhospitability. Polyphemus's refusal to give Odysseus a gift, and his subsequent ill-treatment of the men is would have been a serious affront in ancient Mediterranean society.
Of course, he and his men are understandably horrified when he kills and eats two of their comrades. Further, he is struck by the fact that Polyphemus declares his total lack of respect for the gods. What is more, Odysseus (with good reason) sees Polyphemus as simple-minded. He is amused by the ease with which he is able to outwit the stupid beast, who he views as a murderous savage. In the context of the story, the encounter with the Cyclops is an example of how Odysseus's wits overcome brute force and brawn. On the other hand, his insistence on revealing his identity to the blinded Polyphemus is a famous act of hubris that lands him in trouble when the Cyclops prays to his father, Poseidon, to make trouble for Odysseus on his way home. Ultimately, however, it is the lack of civilization and hospitality on the part of the Cyclops that first angers Odysseus.