Rational means in accordance with the principles of logic, you can't have your own logic..
I'm well aware of that. You confuse logic with objective evidence.
It is not illogical to believe that the future is determined by our choices, whether G-d exists that is capable of knowing what we will choose or not.
It is deceitful to claim that "we have no choice", because G-d knowing what we choose means we will choose it.
The only reason we can't choose other than what G-d knows is because as far as G-d is concerned, we have already chosen it, so He can't be wrong.
It is NOT that He can't be wrong because G-d has preordained it, as you suggest.
Our existence in a physical temporal universe is an objective fact..
..and nobody is claiming otherwise.
..but G-d is NOT a physical person living in this universe.
That is how come He knows what we will choose. While we perceive the future as "hasn't happened yet", He does not.
I don't care whether you consider it a rational belief or not. Time belongs to G-d, and He is its author.