Capitalism is the rock trapping you and slowly killing you. The act of cutting the arm off is the act of Revolution. The act on its own without any context to prompt it is brutal and unnecessary. When the rock traps the arm however, in order to survive, you need to cut the arm off. Socialists, much the same are not violent people wishing for Revenge and riots, but if these are the actions that free the Proletariat, it is necessary. Liberals deny this fact and let themselves die trapped in the rock.