From what I understand (and I may be wrong because people who are advocating rising taxes are not very good at explaining their position), the idea is not to in

From what I understand (and I may be wrong because people who are advocating rising taxes are not very good at explaining their position), the idea is not to increase government income/spending per se. The idea is to redistribute wealth and the government's income is irrelevant (hence the GP's saying it "won't do anything" despite the obvious increase of this income). For all we know a tax increase may decrease the total money collected by the government as the wealthy flee into more favorable tax regimes. This is all right from the point of wealth redistribution (it happens anyways as the local wealth decreases even through different means) but would be unacceptable from the income/spending point of view.