Why do Christians constantly attack the theory of evolution as a crackpot idea?

Because it is a crackpot idea. The only pieces that they have in the puzzle fits in better with a creationist view, and the pieces that don't fit in anywhere, such as logs in what is considered to be millions of years of rock in the earth, or the fact that there are canyons that would have leveled if they formed over a long period, point to a flood, not evolution. Case and point, science proves creation much more than evolution. There are hundreds of pieces missing from the evolution puzzle that I could name. I'd be here for a very long time if I went through all of them.