In order to understand the process of why haters hate, you must understand the definition of a hater. A hater is "A person whose jealousy of another person success or achievements makes them verbally nit-pick any flaws no matter how small or just make up flaws in order to somehow try and belittle the successful person."
Instead of getting mad at haters for hating, keep doing what you do that brings hate your way. Having haters is one way of knowing your constantly doing something right. It's always good to have your name in someone else's mouth, keeps you popular.
Understand that it's in a haters blood to hate. It's not that they hate you, but rather they hate themselves or hate others who have. The distaste a hater has for you will only grow over time If you continue to suceed, so push forward.
The most simple way to deal with a hater is not to deal with them at all. They seems to always posses a negative aura around them and it may rub off on you if you're around them to long, so let a hater do their job, drink haterade!