Therefore, beloved, looking forward to these things, be diligent to be found by Him in peace, without spot and blameless; and consider that the longsuffering of our Lord is salvation--as also our beloved brother Paul, according to the wisdom given to him, has written to you, as also in all his epistles, speaking in them of these things, in which are some things hard to understand, which untaught and unstable people twist to their own destruction, as they do also the rest of the Scriptures. (2 Peter 3:14-16)
But solid food belongs to those who are of full age, that is, those who by reason of use have their senses exercised to discern both good and evil. (Heb. 5:14)
These passages and numerous others tell us, as Christians, that we are expected to grow in our knowledge and discernment to be capable of understanding what is expected of us. This requires objectivity on our part...meaning an unprejudiced look at God's word in every tenant.
An example of subjective speech is found in Titus 1:12..."One of them, a prophet of their own, said, "Cretans are always liars, evil beasts, lazy gluttons." This is an example of racism, which prevents proper discernment because a racist arrives at his conclusions based on his own life experiences. He is taught to hate those who are different than he is. so he develops subjective feelings and look at everything through a prism of those feelings. Verse 13 says "...rebuke them sharply, that they may be sound in the faith." So soundness comes from an objective mind. We can't base our understanding of any scripture on our feelings. We may think we know the way other people think, but we don't.
Another example is found in those who believe in evolution. If one presents evidence that evolution is not responsible for the world we live in, it is usually rejected, not because the evidence is unsubstantial, but because all science, is seen through a subjective prism of evolution. The evolutionist concludes the evidence must be falsified. He believes only evolution is scientific and no supernatural explanation can be entertained. Not until he opens his closed mind can he know the truth.