Because you seem to be trying to establish some equivalence between Anna's circumstances and the author's. I think it's insulting. If I misunderstood the point you were trying to make I apologize.
Is that the relevant thing in terms of causing guilt? Who knows? As I said, I think the only relevant thing is this guy signalling to all the other white people what a virtuous fellow he is.
ergo
the author feeling guilt => absurd
.
the author is being mocked for the absurdity of their feeling guilt. i think the crux of the insult is gentrification guilt is reserved for the privileged.