Asch Conformity Experiment
TLDR; You are strongly influenced to believe what those around you believe.
The Asch Conformity Experiment shows us that even the most obvious truths can be distorted by simply having enough of your peers disagree with you. The discomfort caused by being alone in your beliefs can often cause you to give in and actually reshape your view of reality. Watch the video to see the experiment in action.
As you can see, peer pressure is very powerful. Conformity causes geographically held beliefs. Religions are a common example of this. Given a birthplace, you are more likely able to guess a person's religion. This is because they grew up in families, schools, and communities all holding a common belief system.
The best way to combat this tendancy is to recognize where your discomfort is coming from. Try to differentiate between the discomfort of holding an incorrect position and the discomfort of nonconformity. Embrace your unique positions, and only change your mind when your peers have given you sufficient reasons to.