How we cite our quotes: (Part.Chapter.Paragraph)
Quote #4
The committee had to inspect the untouchables' quarters also. Only one member of the committee was ready to accompany me there. To the rest it was something preposterous to visit those quarters, still more so to inspect their latrines. But for me those quarters were an agreeable surprise. (2.25.10)
This shows just how biased Indians were against the untouchables.
Quote #5
Even here [at the Calcutta Congress] I was face to face with untouchability in a fair measure. The Tamilian kitchen was far away from the rest. To the Tamil delegates even the sight of others, whilst they were dining, meant pollution. So a special kitchen had to be made for them in the College compound, walled in by wicker-work. It was full of smoke which choked you. It was a kitchen, dining room, washroom, all in one—a close safe with no outlet. [...] If, I said to myself, there was such untouchability between the delegates of the Congress, one could well imagine the extent to which it existed among their constituents. (3.13.11)
In other words, the congressional delegates hadn't yet gotten over untouchability, so Gandhi is saying the people they represent must be even more prejudiced against the untouchables.
Quote #6
Some of the classes which render us the greatest social service, but which we Hindus have chosen to regard as "untouchables," are relegated to remote quarters of a town or a village, called in Gujarati dhedvado, and the name has acquired a bad odour. Even so in Christian Europe the Jews were once "untouchables," and the quarters that were assigned to them had the offensive name of "ghettoes." In a similar way today we [Indians] have become the untouchables of South Africa. It remains to be seen how far the sacrifice of Andrews and the magic wand of Sastri succeed in rehabilitating us. (4.14.1)
Gandhi compares the plight of the untouchables to the ostracism faced by Jews in Europe and Indians in South Africa. It seems as if everywhere, some group of people are discriminated against.