Somebody made the same remark on Facebook and I wrote:

As I've written elsewhere, the cost-effectiveness figures in the Washington Post article are wildly inaccurate, but if nothing else, one can give to GiveDirectly http://en.wikipedia.org/wiki/GiveDirectly. If someone in finance makes $500k/yr and donates $300k/yr to GiveDirectly, they're giving 270 African families about a years' worth of their income, every year. The harm that the finance work does would have to be really big to outweigh that.

There are people who did more damage than they could make up with charity (doing harm way out of proportion with their earnings), but I think that they're rare.