We create laws because people cannot be relied upon to do the right thing. We have laws to protect us from murderers and rapists and to punish those breaking laws.
Greed in this country has become excessive for some people and corporations. When the CEO of a company makes more money in one second than his workers do in one hour and insists that providing healthcare would 'bankrupt' his company, it is an example of the corporation or person taking advantage of his workers.
Greed, to the point of requiring full time employees to apply for food stamps because it is not a living wage, needs to be limited. This is not an attack on capitalism but an attempt to punish greed when it harms others substantially.