Christianity relies heavily on in-group type behavior and thinking. This is one of many excercises to constantly affirm who is "with us" and who is "not with us" or at worst "against us". It helps keep people in the fold.
"A casual stroll through the lunatic asylum shows that faith does not prove anything." -Friedrich Nietzsche
"All thinking men are atheists." -Ernest Hemmingway
"Those who can make you believe absurdities can make you commit atrocities." -Voltaire
"All thinking men are atheists." -Ernest Hemmingway
"Those who can make you believe absurdities can make you commit atrocities." -Voltaire