Well, it depends on the context you are dealing with. Ignorance at a workplace is unacceptable. A person ignorant of his own field is unacceptable. A person who doesn't have the basic knowledge about his own country is provocative (Especially the ones in our country who doesn't know the difference between the southern states)

But can you get angry on a person who has no musical background for not knowing a particular musical note or the one who doesn't know baking for being ignorant of a particular baking tip?? Or a person who has no interest in painting saying he have never heard about your favorite artist??  Its natural for people to ignore things that are of no interest to them. 

You can't expect everyone to know everything. Everyone is in the process of learning throughout their lifetime.