Seriously, though, isn't the rationality behind predestination something like "If God is all-knowing and all-powerful, it's foolish to suggest we're capable of making decisions or doing anything he doesn't know. Because there's NOTHING God cannot do and NOTHING God doesn't know." But isn't that also an assertion of God's limitations? You're saying God COULDN'T grant us free will beyond his sight. Which, to me, seems like a greater shackle than saying "God doesn't know the next decision I'll make because I have free will by his design."
Reminds me of my favorite, Chuck Norris joke:
How powerful is Chuck Norris? Chuck Norris is so all-powerful he made a rock so big even he couldn't lift it... THEN HE LIFTED IT ANYWAY JUST TO SHOW YOU WHO HE IS!
But seriously, the "can God make a rock so big even he can't lift it?" is a question we all had to reckon with as Christians at some point in our faith.
To me, the simple answer is no, he can't.
Does that mean God is not all-powerful?
No. God also can't make a squared circle or other things that contradict his creation at base.
But you know what else is part of God's creation?
Free will.
That's as much a product of his creation as anything else within the spectrum of his creation.
To say we have free will isn't placing a limitation on God's power any more than saying he can't make a rock so big he can't lift it or he can't render a square circle.
All are products of his creation and, thus, better understood as limitations of that creation than limitations upon God himself.
So yea, I believe in free will because I believe it is but another endowment of God's construction.