Look, neither of us might agree on a young Earth, but be careful about dismissing Christians who believe this out of hand. It is certainly possible to believe God created a mature Earth, and still have a strong belief in science. Not every person who believes God created Earth 6000 or so years ago denies climate change, or smoking v. cancer, or the logic and necessity of vaccinations. Some Christians who believe in a young Earth also accept evolutionary processes are real, even if they don't believe humans evolved from apes.
Attacking the reasonability of Christians and immediately rejecting every person who believes in a young Earth as crazy is neither fair nor productive. Many Christian perspectives and opinions are absolutely valid and reasonable even if we disagree with them