Summary: Itachi loves his clan, but he loves peace more.
Itachi loves his brother. Itachi loves his father, his mother, his family, his clan. Itachi loves Konoha, loves his Hokage, loves being a loyal shinobi. But of all the things he loves, he loves peace the most. And so he kills his clan; his traitorous, rebellious clan who would have brought war to their village, their home. He slices effortlessly through their bodies, each slash of his sword a nick at the love of his heart. Tonight he will be 'traitor', be 'clan killer'. He will denounce Konoha, denounce the Hokage, denounce being a loyal shinobi; even though every corpse on the ground screams his loyalty to the last.
Itachi kills his clan, kills his family, kills his father, kills his mother, kills his place as the Hokage's right hand man. Itachi loves his village and his clan, but he loves peace more, and he will destroy his bonds a thousand times over in order to see those he loves safe.
Itachi leaves the village. And as Itachi leaves the village with tears streaming down his eyes, he has to reorganize his priorities; he loves peace, but he loves his brother more; he cannot kill his brother, not even for peace. He lets him live.