Why? Do you also doubt the accuracy of the account of the Sermon on the Mount, even assuming that it is a summation rather than a word-for-word transcription? On what basis should we living in this century doubt the accuracy of the attributions in the generationally contemporaneous writings of people who were there at the time, who claimed to be eyewitnesses, and who went to their death sticking to their account of the empty tomb? I'm not talking at this point about believing the claims themselves, but merely about the general accuracy of the accounts of the claims. If he didn't make the claims why did the Jewish religious leaders want to kill him? Were there not nutcases at the time who ran around claiming to be the Messiah?
Have you ever doubted the authenticity of the sayings of Homer, (not Simpson) Socrates, or Buddha?
Jesus taught that not everyone was a son of God in the unique sense that he was. He told the Pharisees, for example, that they were of their father the devil. How can a good teacher teach people that there is a supernatural devil, and that they are his offspring, if in fact there is no such bean?
Cordially,
My doubts are enhanced by the fact that those spreading the word of these teachings had an agenda of conversion, and knew the claim of a miracle here and there would enhance business.
But the final product, whatever the changes, substitutions, add-ons, etc.. is still pretty darn good, IMHO.