It seems that many Christians today fail at this: They speak of non-Christian literature as if they expect Christian value out of it and become disappointed if that is not the case. They then speak of Christian literature as if they should justify non-Christian value out of it and become offended if it is criticized.
Beware of what is right (not what is wrong) from sources that are not of Christian foundation; Beware of what is wrong (not what is right) from sources that are of Christian foundation.