As nexonal first stated, there are many reasons. Here’s one more. I am a faithful man who believes and has reconciled creationism and evolution. That said I believe hate has its origins in the need to survive. I also think racism and ethnic bias are tied neatly together with hatred. Think about it. Long before TV and nearly all other things of life today, early “humans” gathered in small groups, more like pacs of animals(hummm). They needed to, in order to survive and flourish. Imagine a pac, mostly family members, minding their own affairs. For months or years their activities go on. Then one day, they see, for the first time, a group of animals like no other. This group in fact is eerily similar to themselves. Then these new people ravage, rape, pillage and plunder their home. Fortunately or not, a few wittiness and survive.

Now, how trusting, excepting and welcoming to strangers do you think those who made it will be to the next group of “visitors”? I think not. I think hate.

Over time we have evolved, grown,developed and matured. We developed tools like shaking hands, originally with both hands, to show, prove we didn’t possess a weapon.
Ironically, blockchains implement, “Trust, but verify” . Weird right? All this time and we still face this.