Racism
Racism is a perfectly natural human defence instinct that urges us to gather and roam with our own particular herd. It has defence elements supplemented deep within it that drive us to maintain our collective purpose and integrity.
However, that said, it best served its purpose in another age when as travelling groups we depended upon each member to be continuously on their guard for outsiders, who perhaps presented a threat in those primitive early years of evolution.
In today's society of merging races it has no purpose and is rightly denounced as the villain it is.
Given time and the intricacies of evolution it will vanish of its own accord, but for that to occur humankind must continue to instil into its collective psyche its obsolescence.
Like everything else worth the fight, we will as a species get there in the end, provided of course it doesn't destroy us all in the process.
And that is Racism, horrendous isn't it.