I'm going to try to pull all the sub-threads together, and answer the objections here.

History shows that many scientists are indeed closed-minded. Here's a quote from Lord Kelvin, who was a very prominent (and good) scientist, from 1895: "Heavier-than-air flying machines are impossible." Pronouncements like this tend to occur because many people make the mistake of thinking that because something is impossible today, and will probably be impossible 10 or 100 years from now, means that it will always be impossible. This is from one of Dave's responses: "You know what happens when you do an experiment that is repeatable and rigorous, and disproves a long-standing theory?
You win a Nobel Prize."
But what if scientists think so little of the evidence that they don't bother repeating the experiment? Science has a long and sordid history of ignoring evidence that does not fit established theory. Example: the platypus. The platypus would have been "discovered" long before it officially was, had contemporary scientists been worthy of the name. Even stuffed specimens were called frauds, simply because they violated what science "knew" had to be true. Another example: one of the great apes--I don't remember which one. Scientists had eyewitness accounts from the native people going back decades, but ignored them because they "knew" that such an animal did not exist.
Dave also mentioned Einstein. But he rejected the idea of quantum mechanics because he didn't like some of the things that it predicted.

Another topic: UFO's. Many scientists will readily admit that intelligent life probably exists elsewhere in the universe. They just don't think that it's visiting us. Why? Because feasible space travel is not possible for the human population, and will not be for many years. Therefore, they flatly state that "true" UFO's cannot exist. They absolutely refuse to consider the likely level of technology that an intelligent species even 1,000 years ahead of us would have. Also, many, many scientists will not admit that just because something is theorically impossible now does not necessarily mean that it will always be impossible. Therefore, all UFO sightings MUST be debunked or explained away. Now I will readily admit that most UFO sightings--perhaps even 98%--are in fact identifiable or explanable. But in their mad rush to discredit all sightings, some scientists will say, for example, that the witness saw Venus without even bothering to check if Venus was visible in that direction at that time. Another example of this slapdash "science" is the Marfa Lights in Texas. A group of sceptics "proved" that the lights are reflections of car lights on a nearby highway. That's a good, reasonable explanation, except for one thing--it ignores the evidence. The Marfa lights were first reported in 1883, several years before America's first car was invented.

And finally, many scientists absolutely refuse to look at or consider studies done on certain subjects, such as UFO's, no matter how rigorously done, simply because the subject is not "scientific."