The perpetrators of negativity often live in a self-absorbed world. They can easily create the things they're trying to cover-up in those they strive to control. It is not unusual for the intolerant person to cause others to be intolerant of them and want to avoid their presence at any and all costs. Yet...there are still people who feed off the "hater" because he, or she, promises them greater control over others, a false higher self-worth, and a feeling of infallibility.
It is sad that people need to "feed" on others in order to feel good about themselves. Teaching love, peace, and tolerance should be the message that is communicated to all children so they grow up loving and feeling secure about themselves, which translates into the ability to pass on that love to their fellow beings. In the same vain, it is also not unusual for adults to have an "epiphany" after living years of negativity. The need to teach love and tolerance is not one that is delineated by age, but should be ongoing throughout life.
We really are one. One species, one group of beings within a larger grouping, one entity living within a greater oneness. The more we are victims of greed, the over materialization of society, the desecration of our environment, divisiveness along the lines of race, religion, nationalities, and other mental constructs, the harder it is for some folks to understand the need for love when all they are taught is that they're not good enough, or in some cases, superior to others. So...they have to buy this to look better, own that to feel better, get a better job than the next person, compete for needless things that are given meaning, set themselves apart, and even mock others in order to feel better about who they are. All these situations breed insecurity and lack of respect for their fellow human being. I'm not saying that it always manifests itself in that manner, but - is does help to breed it.
We must spend some time being introspective and look at the refection of society within us and its affects. Each person has the ability to be a "saint" or the embodiment of "evil." When a person realizes that the best way to love others and be tolerant of others is to understand themselves, be aware that they're not perfect, realize that no one is, and know that everyone else on this planet wants to feel love, respect, and caring...only then will the mirror of humanity reflect an image of peace, love, and tolerance.