This sounds confusing, but consider this. In a typical civilized society, the idea of killing someone is abhorrent. We abhor violence in any form, and killing is one of society's most proscribed evils. But then war is declared, and suddenly, the idea of killing people is not only no longer abhorrent, but condoned and encouraged. The person who does not kill in the name of their country is considered abhorrent - a coward - and is castigated by an entire nation. Then the war ends, and the killers are welcomed home, but told not to kill anymore. Post-Traumatic Stress Disorder ensues.
We still are in the slap-and-tickle stage of understanding and accepting our own sex and sexuality. We giggle and get nervous even when the topic is discussed rationally.