I actually had the conversation a few days ago with a co-worker who is unapologetically socialist. I brought up Thomas Sowell's conflict of visions. I briefly explained my position of a contained vision -- effectively that heaven isn't for this world, people are naturally flawed, and that there are certain aspects of human nature that we can't reasonably hope to change.
I included greed in that assessment. I think that I'm right that people are self-interested. I'm not making any ground-breaking statements. We all know it.
Still, my coworker asked me what the solution was in my dumb, libertarian brain (he was more polite than that). The simplest answer is that there isn't really an answer. We're just trying to work with what is rather than operating under the delusion that we can stomp out every demon of human nature.
Still, I think a better way of thinking about this is to talk about dealing with greed in comparison with dealing with gravity. You can't make gravity not exist. You can't stomp out gravity. Any law attempting to punish gravity for a plane crash would be stupid. No, we learned how to fly by understanding that gravity is a thing and using the laws of physics for our benefit.
The same thinking can be applied to greed. It's not helpful to deny that greed is a constant thing. It's patently absurd to blame greed on an economic bust just like it's absurd to blame gravity for a plane crash. No, you learn to work with greed just like we learned to work with gravity.