Everyone has an ego and one's own opinions are more addictive than heroine. That's the largest obstacle in keeping an open mind . Keeping an open mind doesn't mean giving up your opinions.
Variety is the essence of evolution.
Without it, our minds cannot be challenged, cannot question, cannot advance. We need to argue our opinions. But we also need to listen. If we condemn a group then we run the risk of bigotry. You don't need to agree with everyone but it helps to at least try to understand them.