It seems that its roots lie in the insecurities that people have about themselves and manifests itself in outward ways. Why would you hate someone who has done nothing to you and why would their life impact you in any way if you do not know them?
Much of the world thrives on hate as if it were oxygen. It permeates the pores and gives a raison d’etre to groups who must find enemies to slay lest they look inwards towards themselves and discover their own failings. People of every stripe who don’t fit someone else’s idea of normality will continue to become martyrs of those who themselves need repair but dare not ever look in a mirror.
The evolution of humankind depends of wiping out hatred but so long as there are those who have been traumatized through their own childhoods, it will continue to exist unencumbered by facts. It will fester in places where ignorance and bitterness incubate and find a home in another person ready to do battle with reality.