If Christianity is true then it ought to follow (a) That any Christian will be nicer than the same person would be if he were not a Christian. (b) That any man who becomes a Christian will be nicer than he was before. … Christian Miss Bates may have an unkinder tongue than unbelieving Dick Firkin. That, by itself, does not tell us whether Christianity works. The question is what Miss Bate’s tongue would be like if she were not a Christian and what Dick’s would be like if he became one. …
We must, therefore, not be surprised if we find among the Christians some people who are still nasty. There is even, when you come to think it over, a reason why nasty people might be expected to turn to Christ in greater numbers than nice ones. That was what people objected to about Christ during His life on earth: He seemed to attract “such awful people.” (C.S. Lewis, Mere Christianity [available in full on-line], Book 4, Chapter 10)