Hooberus,
This has been an interesting discussion.
I like your point about comparing macro-evolution with flatearthism: one has been directly observed and the other is inferred by evidence. Let's use another example:
Plate Tectonics. The growth of mountains and macro-movements of continents have not been directly observed, though their tiny movements have been. The logical conclusion is that these tiny movements over time create large macro changes. We no longer hold the belief that the continents and mountains were put in their place by a deity as we see them today. We know that the earth looked much different millions of years ago. We no longer teach old theories that do not have evidence (including a global flood) to our school children. The other theories were either not scientific, or turned out to be wrong.
The same is true with evolution. We all accept micro-evolution. There is no known limiting phenomenon that would 'cap' these micro-changes over time. Logically this means that over great spans of time these micro changes add up to macro changes. The inference is not unjustified and the logic is strong.
Again, creation as an option has had it's day in the science class. That theory lost out - it did not fit observed facts as well as evolutionary theory. That is why there is no reason to discuss creation or intelligent design in a science class room. It would be appropriate, however, to disucuss such subjects in comparative religion, philosophy, and mythology classes.
For example, science teachers no longer discuss Lamarkism as an evolutionary theory - it had it's day and it has been shown to be incorrect. Old, tired, incorrect theories should not be taught in science class as 'valid options'. If a testable theory of intelligent design could be developed and compelling evidence for intelligent design were found, then we should expect to see such subjects discussed in science classrooms.
rem