Fear, failure, suffering, and sin are inescapable components of our fallen human condition, and while we can resist them in this life, they will never be eliminated from "this vale of tears." Heroism and the confrontation of evil—a confrontation most often achieved through suffering—is the only way to truly grapple with the problem. To paraphrase Alfred, we must learn to get back up; to rise again, and press ever forward towards the light.
The Unimpeachable Testimony of Dr. John Watson
Essentially, the good doctor is a character witness. While sometimes bemused at his unshakable faith, we have no doubt about the veracity of his insights. Our trust of this simple, kind-hearted man and our confidence in his judgment runs far deeper than our distaste for Holmes and his ego-centric tendencies.