James 4:6
...."God opposes the proud but gives grace to the humble."

Satan was cast out of heaven because of His own pride. That story sheds light on why God hates pride so much. It sets man up against God. God created me for His glory and that means that I must experience Him on His terms, which involves me being humble in worship. All have sinned and fall short of His glory and pride seeks self-glory. God hates pride because it seeks to rob Him of His glory and that is an attempt at redefining who God is.

If I don't know God as Lord and King then I simply don't know Him. He is God and He is good, but He resists the proud by His very nature.