Knowledge = narrow, part 2

How does knowledge make you more narrow minded?
If you didn't know anything about history, then you would have a broad mind about the past. You would be able to imagine the past in any way that you saw fit. But if you knew history, then you'll comprehend why things are the way they are and so your mind becomes more narrow. You could still have a big imgination about the past, but you'll know the past and when you have to educate someone about the past it will be the truth, one path.
If you didn't know about what clothes are in or what matches then you'd wear basically whatever you want, but because we live in a society that knows what is in and what matches then we have a more narrow line of clothing, don't we? We can choose to not go with the trend, but it just wouldn't make sense to. We don't wear robes, we wear shirts and pants.
So apply this to important stuff, I just gave examples so you guys could understand what I meant in my last post.