Jesus is 100% God and 100% man.
Jesus (a man) cannot reject or hate the Father. He cannot reject the Father because He too is God, and God is not divided. God is perfect and without sin.
Jesus, not being able to reject the Father, is not disqualified from being a full and true man.
Therefore, it is not a required condition, in order to be fully and truly human, to have the ability to reject God.
Therefore, true love for God from humans is not only possible if humans have the ability to reject and not love God, as some would argue: Love is only real if it is chosen.
If it’s not true for Jesus, it’s not true for mankind.
We should not decide what is required for one to be truly human by looking at ourselves, then applying those requirements to Jesus.
It should be done the other way around: What is required for Jesus to be a human (the perfect human) is also what is required for us to be humans.
Those who argue for human free will often state that humans need free will in order to truly love God — it’s not true love if it isn’t chosen.
The major flaw with that thinking is that it’s not true for Jesus. Jesus cannot reject the Father. Jesus loves the Father perfectly. Jesus is 100% man.
Do humans have free will? Yes, but only after being freed from the slavery of sin. True free will is when sin is impossible.
If you were completely free from sin, you would be unable to hate God. You would be a perfect human, like Jesus.
Related reading: Free Will and Evil