When Jesus sent forth his disciples to the cities in Israel he would come to, he gave them to go without money nor scrip nor staves nor shoes nor two coats. They were to go from house to house, teaching the sayings and commandments of Jesus. See JST Matthew chapters 5-7 and 10.
Their words to the Pharisees weren't "you believe in incorrect doctrines and creeds and historical narratives, and here, I'll tend to THOSE motes in your eyes," and then to argue them into submission, but "why do you teach the law and commandments when you are yourselves the children of corruption? You fake believers - first cast the beam out from your own eye and then you will be able to tend the motes in your brother's eye." That is to say, "repent and keep all the commandments and then you will be able to see clearly to help others." The disciples were instructed to keep the mysteries of the kingdom of God to themselves, telling their unbelieving opposers to ask of God that they may receive for themselves, for what father wouldn't hear his children's pleas? If the disciples were not received, they went on to the next house and after all the houses to the next city. "Whoever receives you receives me," said Jesus, as he sent forth his army of homeless, stinking, broke, religiously-zealous bums to a self-righteously religious, judgemental, and wicked people to find the few who would receive them.
Who would receive such messengers?
Why, those who would receive such messengers are those who were already keeping the word delivered through Moses and the prophets, who were of a kind to take in the homeless, the hungry, the poor, the sick, the afflicted, visiting the imprisoned, clothing the naked, and so forth. To them would be preached the Sermon on the Mount, the meaning of the law which had come before, that by obedience thereto they would be prepared to receive Jesus.
They weren't proselyting so much as sounding the word of God in the ears of all, and letting all handle it howsoever they may, leaving the contentious and the unbelieving to themselves.
It is written that God doesn't change.
In this light, read D&C 84.