Propensities are what makes man man. They can be justified, indeed they are in fact justified. We can't simply ignore this, this is simply a fact. It's no use crying and whining over it, it's time to embrace it and simply mold it to properly hit humanity, instead of killing ourselves.
Yes, the propensities of man are justified, because greed makes people work. Greed leads people to want to produce things to sell, or work to earn money. This is a positive incentive that leads people to make things that they think other people want to buy. When people have enough, they often help others, who benefit from what initially looked like greed.