The fundamental difference between socialists and free marketists is that socialists believe that wealth is taken, while free marketists believe that wealth is created. A socialist believes that a rich person became rich by taking wealth from other people, and therefore the rich person is a bad person. A free marketist believes that a rich person became rich by creating wealth, and therefore the rich person is a good person.
This is the socialist way of getting a pizza. Assume that pizzas are taken, not created. Find someone with a pizza. Assume that person took the pizza from exploited workers. Accuse the person with the pizza of being a rich greedy capitalist and demand that he return the pizza. If he says the pizza is his property, say property is theft. If he says that he has a right to the pizza because he created it, say that is the sort of lie that rich greedy capitalists always tell to justify their ill-gotten wealth. Since he took the pizza from exploited workers and you are an exploited worker, returning the pizza to you is as good as returning the pizza to the original victims. If he refuses to give you the pizza, have him arrested and imprisoned for stealing your pizza. Remember that violence is wrong, so make sure that the police do not injure him unless he resists when you take away everything he has. If you have to beat him up to get the pizza away from him, that proves that he is a violent person and you are not.
This is the free marketist way of getting a pizza. Assume that pizzas are created, not taken. Find someone who is good at creating pizzas. Offer the pizza creator money or some other reward for creating a pizza for you.
Next time you encounter a socialist artist showing a work of art which the socialist artist created, ask the socialist artist whom he took the work of art from.