A Cantankerous Christian?

In the C.S. Lewis book God In the Dock, he was asked if there are any "unmistakable outward signs in a person surrendered to God, and if that person could be cantankerous?  "Cantankerous" is defined as, "bad tempered, tending to argue or complain."  C.S. Lewis made good points in his answer:

"Take the case of a sour old maid, who is a Christian, but cantankerous.  On the other hand, take some pleasant and popular fellow, but who has never been to Church.  Who knows how much more cantankerous the old maid might be if she were not a Christian, and how much more likeable the nice fellow might be if he were a Christians?  You can't judge Christianity simply by comparing the product in those two people:  you would need to know what kind of raw material Christ was working on in both cases.

As an illustration, let us take a case of industrialism.  Let us take two factories: 

    - Factory A with poor and inadequate plant, and

    - Factory B with first-class modern plant. 

You can't judge by the outside.  You must consider the plant and methods by which they are run, and considering the plant at Factory A, it may be a wonder it does anything at all; and considering the new machinery at Factory B, it may be a wonder it doesn't do better." (Lewis, C. S., and Walter Hooper. God in the Dock: Essays on Theology and Ethics. William B. Eerdmans Publishing Company, 2014. page 49)

Judging others based upon appearances is sinful (John 7:24), and measuring ourselves by ourselves is unwise (2 Corinthians 10:12).  Only God knows the hearts of people and the "raw material" found there which requires much miraculous refinement.  Being saved by grace through faith is no excuse to neglect our own sanctification as Christians, for we should live to please God who gave all for us.  This involves us learning to submit to Christ's guidance, instruction and correction.  Reformation and refinement should not be something we look back as occurring primarily at our conversion but things that are taking place today because our fellowship with the holy God reveals our sin; we continue to fall short of God's glorious perfection.  It would be foolish to condemn Jesus Christ because of spiritually immature and sinning Christians, but it doesn't stop people from doing so.  Dear fellow believers, let's not provide easy excuses for people to ascribe folly to Christ our LORD because of our lack of love, grace, Christlikeness or cantankerousness--if that is indeed a word.