Creationist Ken Ham is furious about this because he considers the book a form of indoctrination. Because teaching kids how science works goes against everything Ham stands for:
Yes, secularists know where the battle is in this culture: it’s for the hearts and minds of the next generation. And they are growing increasingly aggressive in trying to capture the next generation — starting from a younger and younger age. That’s why parents and church leaders need to be active in discipling the next generation to stand on the authority of God’s Word from the very beginning. The vast majority of kids, even from Christian homes, go to public schools where in almost all instances they are indoctrinated with secular ideas (really, atheistic ideas) about history and morality from the earliest grades.
Evolution, much like reading and math, isn’t indoctrination. It’s not an opinion. It’s established reality.
Ham would much rather they learn Christian nonsense from a young age:
We can’t wait until kids are in junior high or high school to start teaching them a biblical worldview — we need to do it every single day right from the earliest age possible… it’s essential that we do this training then because it isn’t really in college that most kids begin to have doubts and questions about the Christian faith — it’s as early as middle school!
In other words, kids begin to question their faith when they reach the age of reason.
Religious bullshit won’t hold up well under that sort of scrutiny.
Science, on the other hand, has withstood every challenge for hundreds of years.