No one tried to claim that Gallileo was an atheist when I was in school. As a matter of fact, I’ve never heard anyone try to characterize him as such, much less that he is some icon for atheism. Sounds like a straw man.
Not meant as an insult, but when were you in school? My high school years were 1998-2002. My tenth grade world history teacher taught this version of the story with great relish. She DESPISED Christianity (personal issues) and made no bones about it. She loved teaching us that the flood was a myth and jumped at the opportunity to portray Christianity in a bad light.
As a Christian myself, my faith was somewhat damaged after school. Until I started independently researching and finding out much of what I'd learned in that class was false. In fact, almost everything I learned in high school was a lie or propaganda.
And I'm not trying to build a straw man, as atheists have confronted me with this version of the story in attacks on Christianity. I'm trying to present the claim honestly before addressing it.