Torf,
I can see your concerns, and the truth is, scientists get very jealous of their pet theories.
When plate tectonics was introduced some 30-40 years ago, some geologists just flipped. They gave all sorts of very good reasons why it was impossible (there was no mechanism/energy source, the plates couldn't float sufficiently, etc.) Now, techtonics is proven, observed fact.
While we can't ever go back and observe evolution, we can come pretty close with microevolution. And, aside from some questions regarding punctuated equilibrium, evolution seems to fit the facts we know pretty well.
Alternate that with a creationist "theory" which of course means a Christain Genesis type of creation. Six days doesn't fit with carbon dating and other information we have regarding the age of the earth. Noah's ark has a lot of problems, starting with where's the water to what happened to dinosaurs. Where did Cain's wife come from? To answer these questions you have to start performing some significant mental gymnastics with what is written in the bible. And many of these gymnastics violate other established theories.
Anyway, I could go on, but the question is, what do you throw out? Alot of theories that agree pretty darn well or just the one that doesn't agree? Logic indicates that you probably have a problem with your one theory, in this case, creationism.
Even among theories, there are certain levels of concretness. For example, Einstein's theory of relativity seems to be pretty solid, where as the theories regarding gamma bursts (deep sky thingees) are still hotly debated. The theory of evolution seems to be shaping up as one of the former, which is why I think you see it being "preached" as a scientific law, even though it will never officially be such.
-legrue