Early in the film, Getty is shown personally rejecting every letter he receives that begs for money, saying that if he accepted every request for aid, he'd be ruined. He also gripes about how "parasites" are always asking him for money. At the end of the film, it's revealed that he has a charitable trust for humanitarian efforts that is actually just a tax loophole and hasn't donated anything. So all those "parasites" he writes to have a perfectly good reason to be asking him for humanitarian aid, and his refusal to give away even a nickel is simply his own greed.
Furthermore, by benefitting from the tax break without actually doing charity, it is Getty who is parasiting the poor's existence to enrich himself.
