It's not "minor details" though. If your choices are predetermined for you, you're not the one making the choices and therefore, are following a pre-determined path.
There's no free will. It's really as simple as that.
This is one of the major flaws with our perspective religion. As Maglor touched on yesterday, there's so much pre-programming involved in the fundamentalism in most branches of Christianity, that to most, it's black and white, not allowing for common sense and rational thought. God gave man science and if man uses science to disprove a belief, it is the belief that needs to be altered. Otherwise, we'd all still believe the world's flat with huge dragons waiting at the ends to gobble up those who tried to sail too far.