Velu Annamalai, the source of this spin on Gandhi is an intellectual heir to Ambedkar and the liberation of Dalits movement. Velu Annamalai was Indian/Tamil but moved to New Orleans. I think their is some truth to what Annamalai said about Gandhi but it is also an exaggeration and takes Gandhi's life out of context. Gandhi was working within the South African dynamic. Gandhi in 1940 was not the same person that Gandhi in 1904 was.
Personally, I have read biographies of Gandhi** by multiple authors and I have read history of India also by multiple authors, and in my opinion, the article is a propaganda for Dalits against Gandhi.
** Gandhi is the correct spelling. Ghandi is plain wrong.