The Complete Works of Swami Vivekananda, Volume 7, Conversations and Dialogues, Section 2:
Swami Vivekananda: “Shankara’s intellect was sharp like the razor. He was a good arguer and a scholar, no doubt of that, but he had no great liberality; his heart too seems to have been like that. Besides, he used to take great pride in his Brahmanism — much like a southern Brahmin of the priest class, you may say. How he has defended in his commentary on the Vedanta-Sutras that the non-Brahmin castes will not attain to a supreme knowledge of Brahman! And what specious arguments! Referring to Vidura he has said that he became a knower of Brahman by reason of his Brahmin body in the previous incarnation. Well, if nowadays any Shudra attains to a knowledge of Brahman, shall we have to side with your Shankara and maintain that because he had been a Brahmin in his previous birth, therefore he has attained to this knowledge? Goodness! What is the use of dragging in Brahminism with so much ado? The Vedas have entitled any one belonging to the three upper castes to study the Vedas and the realisation of Brahman, haven’t they? So Shankara had no need whatsoever of displaying this curious bit of pedantry on this subject, contrary to the Vedas. And such was his heart that he burnt to death lots of Buddhist monks — by defeating them in argument! And the Buddhists, too, were foolish enough to burn themselves to death, simply because they were worsted in argument! What can you call such an action on Shankara’s part except fanaticism? But look at Buddha’s heart! — Ever ready to give his own life to save the life of even a kid — what to speak of ” — For the welfare of the many, for the happiness of the many”! See, what a large-heartedness — what a compassion!”
Complete Works Of Swami Vivekananda, Volume 7, Inspired Talks, Recorded by Miss S. E. Waldo, a disciple, Friday, July 19, 1895:
Swami Vivekananda: “Shankara is often called a “hidden Buddhist”. Buddha made the analysis, Shankara made the synthesis out of it. Buddha never bowed down to anything — neither Veda, nor caste, nor priest, nor custom. He fearlessly reasoned so far as reason could take him. Such a fearless search for truth and such love for every living thing the world has never seen.”
Complete Works of Swami Vivekananda, Volume 6:
Swami Vivekananda: “The religion of Buddha has reared itself on the Upanisads, and upon that also the philosophy of Shankara. Only Shankara had not the slightest bit of Buddha’s wonderful heart, “dry intellect merely!”
Complete Works Of Swami Vivekananda, Volume 7, Inspired Talks, Recorded by Miss S. E. Waldo, Wednesday, July 10, 1895:
Swami Vivekananda: “Shankara sometimes resorts to sophistry in order to prove that the ideas in the books go to uphold his philosophy. Buddha was more brave and sincere than any teacher.”
Complete Works Of Swami Vivekananda, Volume 7, Inspired Talks, Recorded by Miss S. E. Waldo, Tuesday, July 9, 1895:
Swami Vivekananda: “Buddha was the only great Indian philosopher who would not recognise caste, and not one of his followers remains in India. All the other philosophers pandered more or less to social prejudices; no matter how high they soared, still a bit of the vulture remained in them.”