Whoever hates his brother is a murderer, and you know that no murderer has eternal life abiding in him (1 John 3:15).
Why would hating someone make you be a murderer? Because your tongue would assassinate him, and you would whip him with your words until his reputation died. Those you hate, you don’t leave alone. You grind them into the ground like a body, dead, and buried. Your eternal life rides right along and is buried with the body.
The only reason for living this life on earth is to take advantage of the opportunity to be born again, which delivers you to your eternal life with God. That eternal life is filled with love, and it begins at the moment of your new birth. If you are busy hating somebody, that means you are not busy loving Jesus and loving people for Him. It also means that the eternal life which Jesus gave you is not alive in you. Love is what has died.
You can’t afford to hate. The person may well deserve your hatred, but if you hate him, you will deserve the punishment of love deserting you. Nurture your eternal life by living in eternal love, no matter what the cost.