Quoting Michael Parenti’s Dirty Truths, pages 39–40:

The political mainstream is frequently characterized, by those who occupy it, as a democratic force fighting a war on two fronts against the extremes of Right and Left. However, a closer reading of history tells us that the Center has been more inclined to make common cause with the Right against the Left rather than oppose both with equal fervor. Far from being a blameless victim when fascism emerges triumphant, the Center is an accomplice.

In Germany, as early as 1918, the Social Democratic leader Ebert entered an alliance with Field Marshal von Hindenburg “in order to fight Bolshevism.” Throughout the Weimar Republic, as Franz Neumann records in his book, Behemoth, “every law aimed supposedly against both Communists and National Socialists [Nazis] was invariably enforced against the Socialist party and the entire left, but rarely against the right.” Those leftists who were critical of the illegal rearmament of Germany found themselves charged and tried for treason, while rightist assassins and putschists “were either not prosecuted at all or were dealt with lightly.”

The collusion between Center and Right is understandable. Despite their differences in emphasis and methods (differences that are not always to be dismissed as insignificant) the Center and Right share a common commitment to the ongoing corporate class structure, and conservative institutional authority.

(Emphasis added.)