A small part of a much longer argument/post by Simon Wren-Lewis:
More asymmetries: Is Keynesian economics left wing?: ...So why is there this desire to deny the importance of Keynesian theory coming from the political right? Perhaps it is precisely because monetary policy is necessary to ensure aggregate demand is neither excessive nor deficient. Monetary policy is state intervention: by setting a market price, an arm of the state ensures the macroeconomy works. When this particular procedure fails to work, in a liquidity trap for example, state intervention of another kind is required (fiscal policy). While these statements are self-evident to many mainstream economists, to someone of a neoliberal or ordoliberal persuasion they are discomforting. At the macroeconomic level, things only work well because of state intervention. This was so discomforting that New Classical economists attempted to create an alternative theory of business cycles where booms and recessions were nothing to be concerned about, but just the optimal response of agents to exogenous shocks.
So my argument is that Keynesian theory is not left wing, because it is not about market failure - it is just about how the macroeconomy works. On the other hand anti-Keynesian views are often politically motivated, because the pivotal role the state plays in managing the macroeconomy does not fit the ideology. ...