Jacob 7

As Jacob was confronted by Sherem, where Sherem denied the Christ and challenged Jacob concerning his  -

"...preaching that which ye call the gospel, or the doctrine of Christ."  (Book of Mormon | Jacob 7:6)

...it was Jacob's response that caught my attention saying -

"...Believest thou the scriptures? And he said, Yea.
11 And I said unto him: Then ye do not understand them; for they truly testify of Christ. Behold, I say unto you that none of the prophets have written, nor prophesied, save they have spoken concerning this Christ."  (Book of Mormon | Jacob 7:10 - 11)

Jacob obviously taught some logic to Sherem's contention.  But it is what Jacob next said next is what I consider a great example in receiving any non-believers challenge -

"...this is not all—it has been made manifest unto me, for I have heard and seen; and it also has been made manifest unto me by the power of the Holy Ghost; wherefore, I know if there should be no atonement made all mankind must be lost."  (Book of Mormon | Jacob 7:12)

It is the bearing of one's testimony that can never be challenged.