Odysseus could not decide whether or not to kill the Cyclopes or not. The reason behind this was due to the stone being a block for the people inside of the cave. The stone was used to block Odysseus from getting inside the cave and harming others. So therefore that was the cause of him rethinking if he was going to kill the Cyclopes.
The small people were trapped in the cave. So he he devises a tempting plan. Which happened to be going past the he Cyclops eye and having his men escape from the monsters place.
The theme is "you shouldn't prejudge something, by its outward appearance alone." The cyclops was outdone by the smaller people. In the story it states, "I took the woolliest ram, the choicest of the flock, and hung myself under his kinky belly, pulled up tight, with fingers twisted deep in sheepskin ringlets for an iron grip.