They don't! Most atheists use science as an excuse/argument against religion
It wasn’t science that first made question the Bible and church teachings, and that made me agnostic.
It was the passage in Matthew 1:22-23 that changed my view, not physics or biology.
Originally when I read the Bible at 15, and read Isaiah’s sign (Isaiah 7:14), then the Matthew’s version of the sign, I had accepted the gospel’s interpretation and church interpretation that the sign relates to Mary’s pregnancy and the child being Jesus, as the sign of the messiah. I didn’t question these “Christian interpretation” and didn’t bother to double check it.
I was young back then, so I took anything I read at face value, and believing without double checking.
It wasn’t until 19 years later (I was 34 years old in 2000), that I bother to re-read both Isaiah’s passage and Matthew’s passage.
When I read the whole chapter of Isaiah 7, I came to realisation that the author’s interpretation was wrong. Wrong because Isaiah’s sign had nothing to do with Mary and Jesus. And wrong because it had nothing to do with any messiah.
Judah was at war with the Israel-Aram alliance, besieging Jerusalem at that time. Ahaz sent message to the Assyrian emperor, Tiglath-pileser to save his kingdom.
The sign had to do with Assyria’s intervention in the war.
There was more to the sign than just verse 14. When the boy reached certain age, the Assyrian army will invade and conquer both Israel and Aram, taking Samaria and Damascus.
The whole sign is this:
“Isaiah 7:14-17” said:
14 Therefore the Lord himself will give you a sign. Look, the young woman is with child and shall bear a son, and shall name him Immanuel. 15 He shall eat curds and honey by the time he knows how to refuse the evil and choose the good. 16 For before the child knows how to refuse the evil and choose the good, the land before whose two kings you are in dread will be deserted. 17 The Lord will bring on you and on your people and on your ancestral house such days as have not come since the day that Ephraim departed from Judah—the king of Assyria.”
The sign is that Assyria will come (7:17), when the child (Immanuel) is old enough to eat curd and honey (7:15), but before the child could distinguish good and evil (7:16).
Who ever wrote the gospel of Matthew, had cherry-picked 7:14 to give new meaning to the sign. And it isn’t the only sign that the gospel had quoted from the Old Testament to be wrong.
To me, I now recognise the dishonest quotings, to be nothing more than propaganda.
It was this sign that made me reconsider the integrity of the gospels, not science, and certainly not evolution.