"I do not teach the foolish traditions of your fathers, and... I do not teach this people to bind themselves down under the foolish ordinances and performances which are laid down by ancient priests, to usurp power and authority over them, to keep them in ignorance, that they may not lift up their heads, but be brought down according to thy words. Ye say that this people is a free people. Behold, I say they are in bondage. ..."Yes, I can relate to the agnostic Korihor. Only about 12% of the population belonged to a church in Joseph Smith's day, and mock conversations between preachers and these "anti-Christs" were a popular rhetorical device, published in pamphlets in evangelical protestantism at the time.
B. H. Roberts noted the similarity in the stories of Sherem and Korihor, supposedly 400 years apart and written by different authors. Roberts wrote: "The two Anti-Christs--Sherem and Korihor--the stories of their belief and the treatment of them, how alike they are! ... They are all of one breed and brand; so nearly alike that one mind is the author of them, and that a young and undeveloped, but piously inclined mind. The evidence I sorrowfully submit, points to Joseph Smith as their creator."
I guess I don't know why you're asking the question. It doesn't seem particularly noteworthy to me that Joseph was familiar with the arguments of the various sects and non-religionists of the time.
See Grant Palmer, "An Insider's View of Mormon Origins," p. 125-30.