I've come to the conclusion that 90%+ of hate is really fear.
All the arguments I hear, like unfamiliarity of cultures, appearance, or habits, really boil down to fear.

Definitely a common rule of nature. If the wonderfully gifted god made us I have to ask why did he not give us photosynthesis. Plants have it and do well. We as an animal must kill living tissue and then consume it inorder to survive. So we hate or express the attitude necessary to harm It is just mother nature. Or a real stupid god.

I think people hate what they're taught to hate....without a director...people don't inherently hate....

Jealousy is a factor.

Testosterone

Because love isn't everything.

Self-preservation leads to fear leads to hatred of those perceived to threaten our self-preservation. By birth we are allocated a group (race, creed, nation). We are taught that other groups threaten our liberty and therefore we should fear and hate them. We are convinced of this to such an extent that we sanction taking their liberties from them, even their right to life. We are convinced of this to such an extent that we bomb and invade countries that would never bomb or invade us (though we allow ourselves to be convinced individual terrorists do it on their behalf, to ease our conscience and allow our group leaders to kill on our behalf.) Why do we hate? Because we are gullible fools. ?

Becuase the collective IQ of the planet is not very high?☺

First comes erroneous, untrue thoughts and judgments about other people, and this fosters anger, fear, hatred, and generally poor health, loneliness, and unhappiness. The effect snowballs, with ever increasing effects. The solution is to think only true thoughts. Police the mind.

The greatest human to walk the earth in my lifetime was Maxie Maultsby Jr. That is just my opinion of course. His books should be in every home, school, and library.

Because happiness needs a balance? I don't know.... good question...

I agree with all the others on the fear factor.

I heard a correlation just recently, which probably applies to the nationalism we see in the US and around the world: as formerly oppressed populations start to make gains in equality, the establishment populations start getting a little cranky.

I don't know about others, but I believe it comes from the fear basis. They don't know, so they fear.

Agree - fear.
Good book - the Tyranny of Malice - Joseph Berke delves into it a bit.

There would be no hate...if there was not first fear! Fear comes before hate! It is either a known or unknown fear of something! When we know ourselves, we tend to make sense of our fears and they do not become hate...even if we are angry.

We hate because we have fallen prey to the notion that the object of our hatred is made of its negative parts. Hate is a kind of spook for that reason.

Fear.

Fear of change, fear of the unknown, fear of being wrong, and fear of being less than.

selfishness

There is no one answer. Sometimes, it is ecause the persons DNA hard-wired the person to be a vicious sociopath. In other caswes it is due to a twisted personality development. Some cultures harbor much hatred. Sometimes is is a mixture.