But a book smart person could tell you exactly what to do. They could answer your book questions and tell you what different denominations or styles of christian faith would advise you to do.
So the intellectual help of such people can be great! My ex-boyfriend is like that, he is a student social sciences who has a great interest in religious ideas, he knows a great deal about the teachings of the Bible, he just never believed in God, so he never went through anything that we would consider "repentance" (though he always tries to be a good person). He helped and encouraged me greatly on my way with God when I became a believer.
So I still think we can't judge the character of such "unrepenting" book smart people. And their opinion can be helpfull. Opinions are somewhat cognitive things, and knowing the scriptures provides the information input necessary for cognition. So why shouldn't they be capable of a usefull opinion?