Is it fair to have higher expectations of people who are professed Christians?
There's a song that I learned in church camp many years ago. The chorus goes "And they'll know we are Christians by our love, by our love. And they'll know we are Christians by our love".
A true christian should be held to a higher standard. A true christian lives by higher morals hence his exact knowledge of God's word. "For God's will is that all sorts of men should be saved and come to an accurate knowledge of truth." (1timothy 2:4)