I think it might be good to distinguish being "open-minded" from being "flexible". Being N means a person will tend to be more open-minded while being P means a person will be more flexible.
So NJ's for example are quite open-minded. This is because they are very imaginative. If you describe something unfamiliar to them they will be open to listening and digesting the new idea, because their imagination will help them to understand something totally unfamiliar. On the other hand once an NJ has decided the way things ought to be, then they won't readily change course in the same way that a P will. This means they are not particularly flexible. Usually an NJ needs time to reflect on their own to change the course they're on while P's do not.
On the other hand SP's are usually not exceptionally open-minded. If you try to describe something totally unfamiliar to them, they will often get bored or give you a funny look like you're crazy/retarded. On the other hand if you demonstrate this new concept to them they will readily grasp it and will not be so opposed or disinterested. SP's are very flexible and will readily change themselves to adapt to the things in their environment. So in this way a person can say that SP's are open to new experiences, but they might not be so open to new ideas especially if they are some abstract theoretical thing that can't be readily seen in the world around them. So I'd simply describe this as very flexible but not exceptionally open-minded.
I hope that makes sense. It's all semantics really, but I'm trying to explain what the meaning behind all of the semantics is.
And this is very good as well:
You're being too reductive, it isn't just the difference between gullibility and paranoia. If one were to be reductive about Intuition, there's a better one at the bottom of that page:
Ni: Seeking context by avoiding observation
Ne: Seeking context by following observation
Ni is about considering all the possible interpretations of something. It's about finding a way of looking at things that doesn't show itself through typical observation. You don't become aware of these perspectives through interaction, because you can't find them in the outer world. It's like changing the lens on a camera; they allow you to perceive and interpret the world in a slightly different way.
Ne is about actively seeking a greater context in the outer world, and feeds off actual observation and participation. It's about finding hidden possibilities for action and meaning through outer context. The only time you would reinterpret something is when new, related information comes to light through an act of discovery.
Perhaps you're confusing one (or both?) with their sensate counterparts, which don't concern themselves with context at all.