Mr.Partha, everyone has a right to question, discuss and criticise a fellow human being including our great leaders. Like two sides of a coin, they are also humans. While you have quoted three lines related to Gandhiji in South Africa, I'm quoting some snippets too.
One has to read the history of Natal state. Transvaal and Orange free state to understand the political environment in present-day South Africa with respect to Indians and the discrimination they had to face. 1893 was the year in which there were plans to curb the Indian merchants/migrants.In 1894, Gandhiji was requested by the Indians to help them fight the bills passed to restrict Indian trades and their rights. Gandhiji spent the next twenty years fighting injustice.
If you read Gandhiji's life in South Africa between the phase of 1893-1896 and then from 1896 -1914, he has done wonders including helping the Indians with their legal problems without taking any fees. One should also read his discussion with Thillaiyadi Valliammai, a 16-year-old girl who became a martyr during the struggle, he met her after her imprisonment and just before he left South Africa, Gandhiji paid homage to her at the cemetery.
Jan Smuts, a high ranking officer interacted with Gandhiji over many years, when he was gifted by a pair of slippers by Gandhiji, Smuts said, I am not worthy enough to stand in the shoes of so great a man... I had the highest respect for him...
If a colonial, 'white man' who disliked Indians, could understand, be humbled and have respect for Gandhiji, can't we as Indians take a leaf out of Smut's book and respect our own father of the nation?