That's just it; you can never placate people who want to expropriate everything (or close to everything) from others. It's just never enough.
Attempts to tax people at 70% in France (even if it was marginal tax) went south very quickly. Incentive matters a lot because good work is really really hard.
Funny enough Gates seemed alluded to this on some interview I watched a while back.
Being a philanthropist shouldn't justify a low tax rate.