God foreknowing the choices we would make with our freewill, does not mean we do not have freewill. Therefore, God can say, even before someone is born, that He hates them, just as He can say that after they've lived a full life and died. Foreknowing does not take away someone's freewill. For example...
I am in the other room, and hear the cookie jar rattle. I know that when I go in the kitchen that I will find my daughter eating a cookie. Does that mean I forced her to? Of course not. Or again, let's say I'm at the train station, and see a train about to pass by. If I foreknow that the person driving that train will pass me, does that mean he had no freewill to do so? Of course not. Foreknowing what another will do does not take away their freewill decision to do it. God foreknew Judas would betray Christ, it was prophesied, but it was his freewill decision. And God can say He hates him before God even created the world.
Now another mention...
When God hardened Pharaoh's heart, it does not mean Pharoah was a puppet with no freewill. Example; if I throw a ball up in the air, and it bounces off my head, I can make the statement "God bounced a ball off my head." How so? God created gravity, physics, cause & reaction, me, the earth, etc. God set reaction in nature. It is human nature, when someone wrongs you, to react with revengeful thoughts, and to close off your vulnerability so that people can't hurt your heart again. The heart becomes hard and callused, and mean "I'll hurt you before you hurt me."
BUT a heart led by the Spirit does not have natural human reaction. When hurt, it forgives, and even cares for the one who hurt it. "Father please forgive them, they don't fully understand what they are doing."
So whether a heart responds with hatred or with love, is that heart's freewill decision. But both choices are put there by God. I can throw a ball up in the air, and quickly move out of the way, or block it with my hand to keep it from bouncing off my head. My point is we do have freewill choices to make- which will determine which reaction God has set in place.
Cause: If we do not obey God, Reaction: we go to hell.
Cause: If we obey God, Reaction: we go to heaven.
Just because God created both of these causes and reactions, does not mean we do not have freewill choice.