They put him under arrest for violating an agreement he signed saying he would teach it as a probability, not a fact. How smart is it to flip nearly 1500 years' worth of accepted religious AND scientific knowledge based on the specious observations of ONE man? Galileo himself couldn't PROVE beyond *doubt* that he was right--by our standard, he was just MORE right than Ptolemy. Not only did Galileo teach it as fact (again, not something he could PROVE and something he said he wouldn't do), he then ventured into the realm of theology. Catholics and Protestants alike read Genesis as meaning the Earth was the center. True, the interpretation was wrong--but WE know that now. THEY didn't.
It was "heresy." I'm sure you realize that "heresy" only means "An opinion or a doctrine at variance with established religious beliefs." Christians taught that the Earth is the center--that was an established belief. He was tried in a Church court for teaching something different from espoused belief.
Check out this site for a good presentation of the myths:
http://www.griffithobs.org/IPS%20Planetarian/mythofgalileo.html
The crux of the issue is that Galileo was not tortured (as is claimed), he was not executed, he was not exiled; he lived comfortably until his death, even (as the above site points out) publishing his best work while under "house arrest."
As for Copernicus, he did exactly what Galileo had the opportunity to do--"Here's an idea, this looks right." If Galileo had come along and said "I've seen it, here, investigate," I doubt there would have been any trouble. This quote sums up the issue nicely:
"In confronting a theory like Darwin's, Catholics should anchor themselves in the proposition that there can be no real conflict between faith and science. The danger occurs when scientists trespass into theology, or vice versa. The Galileo affair is a sobering reminder of what can happen when certain parties in the Church resist a scientific hypothesis on a priori biblical grounds. If the congregation of Cardinals that condemned Galileo had paid more attention to Augustine and Aquinas, who both held that the Holy Spirit, speaking through the sacred writers, was not teaching a system of astronomy, the disastrous split which occurred between religion and science in the seventeenth century might have been avoided."
http://www.catholic.net/rcc/Periodicals/Issues/Darwin.html
The point about Copernicus is that the Church is OBVIOUSLY not an enemy to science or opponent of change. It merely wants to proceed judiciously, with as much knowledge as possible. Which is why the Church doesn't *support* or *oppose* evolution--we don't have enough EVIDENCE to destroy it or cement it.