This quote accurately describes the effects of hatred. Hatred is a poison to our souls. It causes us to become the very thing that we hate. Most people hate because they (or someone else) has been wronged - that wrong can be real or imagined. A person who hates believes that they have not been treated fairly. This hate blinds us and causes us to treat the person that we hate unfairly - so we become that which we hate.
Now I want to state that I have never hated anyone passionately. However that may not be true. In fact it would be just a denial of the truth (and I would really like to deny this truth because good Christians do not hate). I can think of a person in my who I really loathed, I would like to say that it was not hate (more denial?) My feelings toward this person did exactly what the quote said it would do. It made me treat them unfairly - always expecting the worst and always seeing the worst. It made me blind to possibility that they could change. It truly closed all the doors of thinking. Yahweh took me on long journey to forgive this person and to learn to love them.
An interesting note about this quote. It comes from Saddam Hussein. You know that evil dictator who is sentenced to hang. In light of his execution he wrote a letter. In the letter he stated the above quote and also said "I also call on you not to hate the people of the other countries that attacked us". I was a little bit shocked to hear Saddam say these things. But then I realized that I really know very little about him and everything that I do know comes from the media.
You can read about it at cbc. (By the way I found it some what interesting that this story is already off the front page of their website)