Click here to access article by Jerome Roos from Reflections on a Revolution.
The author sees through the ruse of a civil war between two extreme factions which ruling capitalist directors would like to use as a cover for a police-military crackdown on all dissent. The quote by Sinclair offers a useful political equation to suggest that capitalism will resort to murder whenever their other strategy doesn't work. Their other strategy is obviously liberalism. Thus, I think it logically follows that capitalism minus murder equals liberalism. In both equations I see capitalism as a constant, while the independent variable is the legitimacy of class rule among the larger population, with fascism and liberalism the dependent variables.
Framing the relationships this way suggests that liberalism is only another facade that hides the exploitative system of capitalism. In university philosophy and history classes liberalism is taken far too seriously as a thing in itself that somehow influenced the rise of capitalism. The agency is the other way around. Liberalism as expounded by Adam Smith, John Locke, David Hume, Jean-Jacques Rousseau, Thomas Paine, etc, whether they were consciously advancing property rights--the core concept of capitalism--or not, their ideas were strongly advanced by key capitalists as a major ideological weapon in the struggle against aristocratic rule. Liberalism was used as a cover to justify the elimination of all barriers to capitalist enterprises and the capitalist class's exclusive claims to the wealth derived from these enterprises. Hence, liberalism was, and continues to be, merely political propaganda and a tool to insure the rule of capitalists.