How does Ivan's progression of emotion advance the themes of Gooseberries?

Ivan, the central character of "Gooseberries," works himself up into a state of passionate indignation on behalf of the poor and the suffering in society as he tells the story of his brother Nicholai. As he explains, Nicholai always dreamed of owning his own farm with gooseberry bushes (just as American might dream of a farm with an apple orchard). He lives extremely frugally to save money and finally marries a widow with money. He half starves her so that she dies in about three years, and he inherits her money. At this point, he can buy his farm.
It is near a river polluted by a next-door gelatin factory, but Nicholai ignores that. He plants gooseberries, and when Ivan comes to visit, offers him the fruit. Nicholai thinks the gooseberries are delicious, but Ivan is distressed because they are bitter. He also feels his brother has turned into an arrogant, self-deluded, small-minded man who lords it over the peasants. As he ponders the gooseberries, he has the epiphany that we can only be happy through deluding ourselves, just as Nicholai has done with his gooseberries. Ivan states:

one never sees or hears those who suffer, and all the horror of life goes on somewhere behind the scenes. Everything is quiet, peaceful, and against it all there is only the silent protest of statistics . . . And such a state of things is obviously what we want; apparently a happy man only feels so because the unhappy bear their burden in silence, but for which happiness would be impossible.

This realization makes Ivan unhappy. However, he may not be that different from his brother, because he uses the excuse that he is "too old" to avoid getting involved in social change. His story and the negative emotions it produces also makes the other guests uncomfortable: they wanted an upbeat, happy tale.
Ivan's denunciation of his brother brings up troubling questions, for we only have the story from his point of view. Yet, right or wrong about his brother, it does seem to be true that happiness, then and now, depends on ignoring the suffering of others. Ivan's emotion of indignation does cause us to think, advancing the theme that we are all complicit in shutting out the pain of others for our own convenience. The point of the story is not whether Ivan is "jealous" of his brother, but the discomfort we are meant to feel at the idea of the poor becoming visible to us.