Put them in a situation where they need to use logic and evidence to understand their environment and where understanding their environment is crucial for their survival, and they'll figure it out by themselves. No one really believes God will protect them from harm...
If you threaten someone in their survival they are likely to get emotional. That's not the best mental state to apply logic.
Suicide bombers don't suddenly start believing in reason just before they are send out to kill themselves.
Soldiers in trenches who fear for their lives on the other hand do often start to pray. Maybe there are a few atheists in foxholes, but that state seems to promote religiousness.
Another monthly installment of the rationality quotes thread. The usual rules apply: