1. The default position that you must start from is that nothing exists. From there you add things to existence based on what you can verify the existence of. Once you have verified all you can, it is then natural to speculate as to what else may also exist to fit the patterns/trends you have observed. This is a very simplistic scientific method and even religion used to understand this.
  2. Religion was, after all, early science -- before we had the means to explain things like weather, stars, birth, and death, the best we could do is assume that it was the work of magical entities called gods, Alfar, Sidhe, faeries, Kami, daemons, spirits, et cetera. We have improved since then and we will continue to improve, no matter how much lags behind.
  3. It is extremely easy to make a claim that cannot be disproven. That is called unfalsifiability, and it weakens the validity of an argument or theory considerably. What needs to be done is to present a falsifiable theory and fail to falsify it. The Theory of Evolution is very falsifiable, but hasn't been falsified. That is why scientists discredit Creationism, not because of a vendetta.
  4. Agnosticism is not a middle-ground between theism and atheism. It is part of a separate spectrum. Everyone is either a gnostic theist, an agnostic theist, a gnostic atheist, or an agnostic atheist. For example, most Christians are agnostic theists: they do not claim to know their deity exists, they instead claim that they believe it exists. Likewise, most atheists are agnostic atheists.