Hey I'm OK with people pointing out my typos. I consider it a favor.
Let me explain in a little more detail. We may be construing terms in different contexts. Let's set the concept of "personal" bias aside. The point is that some possible conclusion has already been decided upon without any reference to a controlled experimental situation. For example, if you check out the full Wikipedia article, consider the example they use ( a coin toss ). In such a situation there is no bias, or at least the bias is eliminated to a reasonable level. It is safe, given two choices, heads or tails, that the coin will land one way or the other about 50% of the time. Similarly in medical case studies it is used in what they call a "double blind test" to eliminate bias.
In the case of a UFO sighting however ( and other transient phenomena ), the conditions are uncertain and non-repeatable. There is no empirically measurable alternate from which to accurately guage probabilities based on the null hypothesis ... so one must be fabricated based on a non-quantified assumption ... essentially a preconceived opinion, hence some sort of bias. The only good a null hypothesis is in these situations is to act as a convenience term that sounds scientific, but isn't.
As stated before, it makes more sense in these types of cases to look at the information first without any preconceived opinion, and follow the evidence where it leads based on investigation.
j.r.