Your ex has told you that he or she hates you and there doesn't seem to be any reasoning for this hatred, I realize just how stressful and frustrating this situation must be for you.
You have obviously tried to figure out why someone that loved you, now is claiming to hate you and you cannot come up with a logical reason as to why they feel so strongly in a negative way towards you.
Just think about how nice it would be if your ex was able to think clearly and to realize that they are still in love with you.
I will explain steps that you can take that will allow your ex to stop hating your guts.
Could your ex boyfriend or girlfriend just be giving you the cold shoulder because they need space to cope with their hurt feelings? It could be that your ex is just hurting so much that they are saying whatever it takes to ensure that you give them some space.
Telling someone that you hate their guts is one way of driving someone away.
I would advise you not to contact them when they are feeling so much emotional pain.
They will learn to deal with their feelings faster if you avoid contact for an extended period of time.
How long should you back away if your ex screams to you that they hate you? The period of time of course varies from person to person.
I would personally wait until your ex contacts you or has stopped stating for around 2 weeks to others that they despise you.