The preacher doesn't care if Jesus was fictional as long as the believers keep filling the collection plates.
The citations listed in the Smith letter are unverifiable since no original documents exist(ed).  Everything cited was written 100+ years later and most was cited in the creation of the Bible and its fictions by a 3rd Century Pope in his monasteries containing the few literate people in the Roman Empire.  All by direction of the Roman Emperor to rid the subjects of the multi-god paganism for a One God dictator more reflective of his own reign.  Judaism was the only One God religion in existence at the time, so it provided legitimate historical basis becoming the Old Testament(with a few? alterations) to introduce the New Testament of the newly created Jesus Christ mythology.  Every change in dogma thereafter adopted the pagan rituals to aid in later conquests of barbarians, i.e., December birth, Spring resurrection, et. al.  The circular logic of scholars reproving all of it.