Answer:
Our political preference generally influenced by the values that we held to determine which one is wrong and which one is right.
Often times, we only socialize with a group of people that only held the same value as us. When this happen,the affirmation that we get from those people will act as external protection that prevent us from hearing the values of other people that do not belong in our social group.
So, External protection of values basically are things that keep us from changing our value that does not come from ourselves.