On September 7, 1937, Mao Zedong wrote a short text called Combat Liberalism (反对自由主义). It lists the kinds of liberal behavior inside the Party. The second is “irresponsible criticism behind people’s backs, instead of making suggestions to the organization.”
“Saying nothing to people’s faces, but talking wildly behind their backs. Saying nothing at the meeting, but talking wildly after it.” (当面不说，背后乱说；开会不说，会后乱说。)