The change of life people experience when they embrace Jesus is awesome and wonderful and miraculous. However, most Christians go to great lengths to prove not sinning is not possible. They believe sin is so systemic that not even Jesus can completely rid us of it, that the righteous results of "humanity and divinity combined" is corrupt and stained with sin. If they're right, then isn't it futile to suggest their experience serves to "prove the reliability and truth of the Bible"? Ellen White wrote:
The leaven hidden in the flour works invisibly to bring the whole mass under its leavening process; so the leaven of truth works secretly, silently, steadily, to transform the soul. The natural inclinations are softened and subdued. New thoughts, new feelings, new motives, are implanted. A new standard of character is set up--the life of Christ. The mind is changed; the faculties are roused to action in new lines. Man is not endowed with new faculties, but the faculties he has are sanctified. The conscience is awakened. We are endowed with traits of character that enable us to do service for God. {COL 98.3}
Often the question arises, Why, then, are there so many, claiming to believe God's word, in whom there is not seen a reformation in words, in spirit, and in character? Why are there so many who cannot bear opposition to their purposes and plans, who manifest an unholy temper, and whose words are harsh, overbearing, and passionate? There is seen in their lives the same love of self, the same selfish indulgence, the same temper and hasty speech, that is seen in the life of the worldling. There is the same sensitive pride, the same yielding to natural inclination, the same perversity of character, as if the truth were wholly unknown to them. The reason is that they are not converted. They have not hidden the leaven of truth in the heart. It has not had opportunity to do its work. Their natural and cultivated tendencies to evil have not been submitted to its transforming power. Their lives reveal the absence of the grace of Christ, an unbelief in His power to transform the character. {COL 99.1}
The first paragraph describes an ongoing experience that serves very nicely to "prove the reliability and truth of the Bible". But this is the very experience most Christians believe is impossible. The second paragraph describes an ongoing experience that reflects what most Christians believe is realistic. But this is the very experience that causes unbelievers to dismiss Jesus out of hand. Ellen White explains it:
The impenitent sometimes excuse themselves by saying of professed Christians, "I am as good as they are. They are no more self-denying, sober, or circumspect in their conduct than I am. They love pleasure and self-indulgence as well as I do." Thus they make the faults of others an excuse for their own neglect of duty. But the sins and defects of others do not excuse anyone, for the Lord has not given us an erring human pattern. The spotless Son of God has been given as our example, and those who complain of the wrong course of professed Christians are the ones who should show better lives and nobler examples. If they have so high a conception of what a Christian should be, is not their own sin so much the greater? They know what is right, and yet refuse to do it. {SC 32.1}