Beliver? Agnostic?

Why is it that when a Christians are talking about agnostics the most common response is disgust? David Dark tells a story of him beginning a class with the question "What is an agnostic?" after receiving answers like "someone who doesn't want to believe" and "someone who chooses not to believe" he was finally able to get the right answer of "someone who doesn't know". From there is stats that not only is he an agnostic but so is his class and the problem is that he thinks that they think that they need to pretend to know in order not to go to hell and that this isn't the case. Why is it that as Christians we feel like we have to know everything in order to get into heaven? that by admitting that we do not understand the Trinity or the Resurrection or the act of Communion we will go to hell, is it because we were taught this or is it a problem that is located among American Christians and our extreme sense of individuality and "be the best you can be"? Before coming to Spring Arbor I was confident in my knowledge, not that I bragged and claimed to know everything but I knew what I knew and was proud of it. After one semester I realized how little I actually knew; after one class with Ken Brewer I had at least 100 new questions running around in my mind. Each question had about 5 follow-up questions and I could not answer a single one of them. After taking Greek it took me twice as long to read a passage from the Bible because I would analyze the verses and try to pick it apart and put in the correct Greek words as well as other English words that could make the meaning more succinct. At times I feel incredibly stupid for having all of these unanswered questions...but isn't that a part of wisdom? Knowing that you don't know everything and accepting that fact whilst at the same time trying to not only answer your unanswered questions but finding even more to ask?