Percy hit it right on the head. On another messageboard, a well-known creationist scientist from AiG posts regularly and his answer as to why evolution was evil was just as Percy stated.
If evolution is true, then there was no Adam and Eve. Without Adam and Eve, there is no original sin and therefore no reason for Jesus to have died for us. And no resurrection, either, meaning no life after death. The only reason Christianity is popular with the masses is the promise of life after death, of seeing your loved ones once again - it's a major tenet of Christianity. Without it, why would anyone believe in God or that Jesus was his son?