Tyler explains to Jack that the first soap was made "from the ashes of heroes." Sacrifice is what allowed civilization to progress. Consider that Tyler also uses many of the same ingredients that he uses to make soap to also make dynamite and explosives. Soap is an obvious cleansing metaphor, but Tyler's true intention is to cleanse civilization itself, largely by obliterating it. His long-term plan to return to a more primitive way of life requires the removal of existing systems of governance and control. Sacrifice will still be required to achieve this, and that is what the space monkeys Tyler has surrounded himself with are for.