The one commonality among all humans is their ability to allow themselves to be manipulated by intolerant historical views and small groups whose best interests involve societal disharmony. Look at the media, which are, ultimately, the government's own, unpaid PR department.
If you turn on any newscast, local or national, on any station you wish, all you hear are stories about all the things that make us different: race, religion, artistic expression, sexuality, etc. The government makes 'issues' of them, feigning concern for the citizenry, which, in turn, fuels the media with inflamitory subject matter. The entire affair plays on the human animal's sheepish ability to swallow anything they are told and not only choose sides, but formulate uneducated opinions. Combine this with the inability to be flexible in their thinking, and you have disharmony by unity.
People learn intolerance from their religion (Catholicism comes to mind, as it says that to even enter another faith's church is a mortal sin), and from their parents. A few years back, nearly 140 years after the end of the Civil War, a town in Georgia vehemently protested the erecting of a statue of Abraham Lincoln, citing that it was a 'terrible insult' to their heritage. People are still burning churches, fearing and generalizing over national origins or skin color, and even protesting the way we express our love of one another. The most infuriating clip I ever had the misfortune to see was of a woman on a talk show talking about how her lesbian daughter 'didn't have to be that way' and how 'she could be re-taught'.
In essence, hatred is a swell born of, nay, synonymous with ignorance. Since ignorance is a dominant trait in the human species, it becomes a unifying factor, drawing similarly ignorant individuals to like groups. The only thing that gives the rest of us hope is our own ability to come together and remain standing before the tide.
