Quote 1
"When I want to take God at his word exactly, I take a peep out the window at Creation. Because that, darling, He makes fresh for us every day without a lot of dubious middle managers." (3.8.24)
Brother Fowles, a preacher himself, doesn't really believe in preachers as evidence of God. He believes in the everyday miracles of nature.
Quote 2
"There are Christians and then there are Christians." (3.8.80)
Here we go: this is probably the main point of The Poisonwood Bible when it comes to religion. There are wonderful people who adhere to the good tenets of Christianity: tolerance, patience, charity, world without end, amen. Then there are those that use religion as a means to power. (See: the Crusades, Nathan Price.)