We grow up learning from our parents. They teach us how to eat, talk, dress up and well behave. What about our beliefs! what is right and what is wrong! how to accept people regardless of their preferences.
Sadly, I realized no matter how parents teach their children all the life-matters, they neglect to teach them how to accept others religiously & socially. And we often see people bluntly throwing judgments and stereotypes at others. Not because they know anything, because they grow up knowing that their parents make the same judgments toward others.
"Open Mindedness" means all the aspects in life. No just accepting what we "prefer" to think is right, and hating what others consider "wrong". I wish if people could make their own judgment and read more books about those certain matters.