How are people taught to be narrow minded??

Via religion; it's the entire principle behind it.

they are taught very little. The more we learn the broader or minds become

1. The aren't allowed to experience many things, all that they know is limited to what they are shown or grown up around.
2. They aren't given a proper education or encouraged to read, study or do well.
3. They are dictated to as children and grow to believe that the only way is the way that they know.
4. Peers that they have are similar minded.. this doesn't help in encouraging kids to learn more, experience more etc.

the list is endless when it comes to willful ignorance really..

limited to certain things. some people cant help sticking to what they know and whats comfortable to them.

That is easy; encourage their fear, nourishand cultivate their egoism.

they grow up in small brains :)