Mighty little force is needed to control a man whose mind has been hoodwinked; contrariwise, no amount of force can control a free man, a man whose mind is free. No, not the rack, not fission bombs, not anything - you can't conquer a free man; the most you can do is kill him.
Robert A. HeinleinTake sex away from people. Make it forbidden, evil. Limit it to ritualistic breeding. Force it to back up into suppressed sadism. Then hand the people a scapegoat to hate. Let them kill a scapegoat occasionally for cathartic release. The mechanism is ages old. Tyrants used it centuries before the word "psychology" was ever invented. It works, too.
Robert A. Heinlein