What is meant by the “plenary authority of scripture”?
It means that we must submit everything we think, perceive or feel – even about Christ Himself – to His external, written Word of scripture.
Here, in a single simple quote, is the best explanation I’ve found.
“To stay away from Christianity because part of the Bible’s teaching is offensive to you assumes that if there is a God he wouldn’t have any views that upset you. Does that belief make sense? If you don’t trust the Bible enough to let it challenge and correct your thinking, how could you ever have a personal relationship with God? In any truly personal relationship, the other person has to be able to contradict you.” ~Tim Keller
Your perception of Christ, professed relationship, and opinion of what He’s about, therefore, carry no weight if they do not fully conform to His external self-revelation and propositional truths of scripture. (2 Tim. 3:16-17)
In fact, saying otherwise is rebelliously delusional.
Pure and simple.
If that disturbs you, then take it up with God. I don’t make the rules, or decide how to reveal them.