When the Baal Shem Tov (Besht) began to teach publicly in 1734, he was opposed by certain rabbinic leaders. The Besht's charismatic leadership and Kabala-based doctrine made them apprehensive. Further, the Besht's insistence on every Jew's ability and obligation to establish a relationship with G-d, regardless of his level of scholarship, led them to fear that the Besht denigrated the need for in-depth Torah study. There were other points of disagreement, but these were the basic ones. Nevertheless, there were rabbis from the "opposition" who recognized the Besht's greatness, as this eyewitness report from 240 years ago by Rabbi Yaakov Kaidener, a well-known scholar and author, demonstrates:
When I was working as a teacher in Yanova, the esteemed chief rabbi of Dubrovna, Chaim Mordechai Margolius, lived nearby. On one of his occasional visits to town, the citizenry came to greet him. He repaid our display of honor by sharing with us some of his original insights in Torah.
Afterwards, the conversation turned to the ways of the Chasidim, and some of those present made snide remarks about several of the great Chasidic rabbis. Eventually they started to make fun of the founder, the holy Baal Shem Tov.
At this point Rabbi Margolius burst out, "Stop this talk! Let not my ears hear such things about this holy angel and precious man! True, I am also one of those who oppose the ways of Chasidism, as is known. You saw that I said nothing till now. Nonetheless, we in these parts do not oppose the holy Besht, G-d forbid. On the contrary: in our eyes, he is just as great as the holy Ari of Zefat!"
When the crowd heard this, they were amazed. They asked, "Rabbi, please tell us who he really was, for we are confused. If he was so great, why do so many denigrate him? And were not his ways unlike those of the great men of the past?"
The rabbi replied, "Your are right; his ways were different, and his teachings were different. Nevertheless, there is no need to be startled by this at all. Even if there could be found a verse in his sermons that seemed to be misquoted, it would still be forbidden to entertain any doubts about his words, for all the letters of the Torah were given into his hands from above, to do with according to his will.
"This can be compared to a great and exalted king who had a beloved only son, whom he loved as much as his own life, and out of this great love gave him all his precious treasures. Once, the king's ministers came to him and said, ‘Our lord king! May you and your son live forever! We know that the king gave his son all the precious treasures, and who can say anything about what the king does; especially since he already did it. Moreover, his son is worthy of this due to his great wisdom and good deeds. But, we cannot understand why your son is arranging the treasures of the king differently than the king-literally from one extreme to the other!'
"The king answered, ‘I gave him these treasures and they are his to do with as he pleases. Besides, I am confident that he is sufficiently wise so as to not cause any harm, and that nothing improper will come from his hand.'
"Exactly the same is known to us about this holy man, the Baal Shem Tov. Once he expounded on the passage in the Talmud [Shabbat 81b]: Rabbi Chisda and Rabba bar Rabbi Huna were traveling in a boat. A certain woman said to them, ‘Let me sit between you.' They did not let her. [It is prohibited according to Jewish law for a woman to sit between two men or for a man to sit between two women.] She uttered an incantation and stopped the boat. They said an incantation and released it."