Capitalism is based on corruption. It's an entire system which says "Hey, guess what - everyone's out for number one, and only willing to help anyone else out only if it helps THEM out more."
And the problem with this is what? Humans are selfish being by nature. We are socially motivated, selfish beings. Just about any and every action a person does can be ultimately traced back to selfish intentions, or mental illness
The system isn't based on corruption, humanity itself is.
I can't pick out one good quote, so instead I give you many (again from Richard Dawkins, because I've not heard of many other people who discuss this topic from the same position (scientific) as he does):
The Selfish Gene (1976, 1989)
* We no longer have to resort to superstition when faced with the deep problems: Is there a meaning to life? What are we for? What is man?
* The meme for blind faith secures its own perpetuation by the simple unconscious expedient of discouraging rational inquiry.
* Today the theory of evolution is about as much open to doubt as the theory that the earth goes round the sun.
* The argument of this book is that we, and all other animals, are machines created by our genes.
* We are survival machines – robot vehicles blindly programmed to preserve the selfish molecules known as genes. This is a truth which still fills me with astonishment.
* I am not advocating a morality based on evolution. I am saying how things have evolved. I am not saying how we humans morally ought to behave.
* Let us try to teach generosity and altruism, because we are born selfish.
* Let us understand what our own selfish genes are up to, because we may then at least have a chance to upset their designs, something that no other species has ever aspired to do.
* They are in you and me; they created us, body and mind; and their preservation is the ultimate rationale for our existence. They have come a long way, those replicators. Now they go by the name of genes, and we are their survival machines.
* No doubt some of your cousins and great-uncles died in childhood, but not a single one of your ancestors did. Ancestors just don't die young!
* The genes are the master programmers, and they are programming for their lives.
* Whenever a system of communication evolves, there is always the danger that some will exploit the system for their own ends.
* ... it is certainly wrong to condemn poor old Homo Sapiens as the only species to kill his own kind, the only inheritor of the mark of Cain, and similar melodramatic charges.
* Group selection theory would therefore predict a tendency to evolve towards an all-dove conspiracy ... But the trouble with conspiracies, even those that are to everybody's advantage in the long run, is that they are open to abuse.
* ... a lion wants to eat an antelope's body, but the antelope has very different plans for its body. This is not normally regarded as competition for a resource, but logically it is hard to see why not.
* What is the selfish gene? It is not just one single physical bit of DNA. Just as in the primeval soup, it is all replicas of a particular bit of DNA, distributed throughout the world.
* ... a gene might be able to assist replicas of itself that are sitting in other bodies. If so, this would appear as individual altruism but it would be brought about by gene selfishness.
* It is normally possible to be much more certain who your children are than who your brothers are. And you can be more certain still who you yourself are!
* The truth is that all examples of child protection and parental care, and all associated bodily organs ... are examples of the working in nature of the kin-selection principle.
* But you cannot have an unnatural welfare state, unless you also have unnatural birth control, otherwise the end result will be misery even greater than that which obtains in nature.
* ... leaders who forbid their followers to use effective contraceptive methods ... express a preference for "natural" methods of population limitation, and a natural method is exactly what they are going to get. It is called starvation.