So here’s a little thought experiment: Imagine that we really did have good reasons for thinking both the Bible and the early church councils to be divinely inspired. Imagine that the Bible made lots of incredibly precise and accurate predictions about the future, and that the councils knew about all sorts of science that they couldn’t possible have known about at that time. So, given that the Bible and the church councils seem to have some kind of divine or higher power behind them, it may be rational to believe what they have to say about hell, the trinity and Jesus.
But of course this is not the situation we find ourselves in, and so both fundamentalist Christians and fundamentalist Muslims are irrational to believe their doctrines based on what’s been passed down through scripture and tradition.