Why was Bhimrao Ambedkar a staunch opponent of Mahatma Gandhi?

There is an archive interview of him on the YouTube channel of BBC News which is dated 26 February 1955. In this he says, “I met Mr. Gandhi for the first time in 1929 through a common friend. That friend advised me to meet him. After this, Mr. Gandhi wrote a letter expressing his desire to meet me. I went to meet him before attending the Round Table Conference. Then he came to participate in the second roundtable conference. He did not come to the first conference. He was there for 5-6 months during that time.” He further says, “Apparently I met him in the second roundtable conference and also had a face to face meeting. After this, after the Poona Pact was signed, he again asked to meet me. I went to meet him. He was in jail at that time.” Bhimrao Ambedkar further said, “Every time I met Mr. Gandhi, I always say that I met him as an opponent. That's why I know him more and better than others because he always showed me poisonous teeth. I was able to peek inside that person, whereas other people would just go there like a devotee and could not see anything. He used to see the same external image which he had created of his Mahatma but I have seen his human form, very clearly.” He further says, “Therefore I can say that I have understood Gandhi much better than the people who were associated with him. If I say frankly, I am surprised that everyone, especially the Western world, took so much interest in Mr. Gandhi. I find it difficult to understand all this because as far as India is concerned, he is just a part of the history of this country, not the creator of any era. His memories have gone from people's minds. The memories that remain are because Congress gives a holiday on his birthday. I feel that if this method of celebrating artificial memories had not been adopted, Gandhi would have been forgotten long ago.”