Here are some talking points off the top of my head:
* Capitalism, not socialism, is mired in old ways of thinking. It's inconceivable that humankind should have progressed so far technologically and, in some respects, ethically that it should remain attached to a primitive economic system that, as even its advocates admit, is powered by the negative impulses of fear and greed -- motives that inherently promote short-sighted thinking, reckless action, waste and social conflict.
* Capitalism is anti-democratic. The vaunted "shareholder democracy" of capitalism does not embody democratic principles; it subverts them. The essence of political democracy is: one *person*, one vote. The essence of shareholder democracy is: one *share*, one vote. This means the corporate CEOs and the wealthy elite who control most people's livelihoods have no accountability to average people.
* There is no such thing as private enterprise or individual achievement. All individual success is of social origin. Every successful business person (or movie star, top researcher, ace ballplayer, whatever) derives that achievement from learning and opportunities provided by society. In essence, every individual in society has equal claim to that society's riches. It's in everyone's interests to see that all individuals develop their talents as fully as possible -- both to maximize the common wealth and to ensure that there are no deprived people to act as a drag on economic productivity and cultural attainment.
* Capitalism stunts individuality instead of promoting it. In order to hold down pay to reward themselves, capitalists try to de-skill jobs and make workers as interchangeable as possible. This results in both boring work and mediocrity of goods and services.
There, I feel like heading to the barricades already!
Carl