Reasoning Behind Hate?

I have a question. Why is it that some people insist on being cruel to others? Is it because they're jealous? Does it really make a person feel better to belittle someone else? To pour salt in someones wounds? Or to make new wounds altogether? Does this truly bring relief to a person?
Some might say that it's a coping mechanism. That a person hurts so badly that the only way they know how to cope with that hurt is to inflict it on someone else.
Maybe it's a form of revenge? That the world is so cruel to that person, and it's unfair. So it is that person's duty, ergo, to inflict pain and cruelty onto someone else. It's only fair, of course.
Perhaps it's because that person feels SO alone in their hurt, that by causing pain to someone else, they can be assured that someone, anyone, is hurt. Good company.

Whatever the reason, though, why cause pain to someone? Everyone is fighting some kind of battle, whether you can see it or not. Don't just refrain from kicking someone when they're down, keep your foot to yourself in any situation. AS HUMAN BEINGS, sharing this great green earth, we should strive to help others. We should strive to offer words of encouragement, not words that will sting or bruise or slice or cut.
We have all sailed upon rough waters. We will all, undoubtedly, sail on rough waters again, and it's our responsibility to make others' voyages a bit smoother.