A believer making the statement “God said it, I believe it, that settles it,” is not much different from a German in the 1930's making the statement “Hitler said it, I believe it, that settles it."
If the God believed in by Christians and other theists is really real (important qualifier: IF), then our critical facilities, which include our common sense and our ability to think logically and rationally, are gifts given to us by God. And if that is the case then using these gifts is much more honoring of God than cringing servile fear of God as of a cosmic tyrant, or uncritical and unquestioning acceptance of anything purportedly said by God in some alleged holy book.
Personal disclosure: I consider myself to be more a
Deist than anything else; I have some reasons that I cannot go all the way with being an atheist. Deists, among other things, reject any alleged revelation from God, such as the Bible or the Koran, as actually being such, and I am fully with them about that.