Open-Mindedness vs. Exhaustive Comparison

Questions about the claim that if Christians really want to be open-minded, they need to read and study other religions before committing to Christianity, and with so many paths claiming to be the sole path, what is to be said about those who choose incorrectly?  

• How would you respond to someone who says, “If Christians really want to be open-minded, they need to read and study other religions before committing to Christianity”?
• With so many paths claiming to be the sole path, what is to be said about those who choose incorrectly?