The origin of ‘baizuo’ (白左) — the Chinese libtard, or ‘white left’
First, the question should clarify what’s actually meant by baizuo (白左) in the Chinese context. The bai appears to come in part from baichi (白痴, a moron), and it’s meant in the same way as “libtard” is meant in the U.S. by certain conservatives. It doesn’t mean “white” (i.e., European or Euro-American) liberals. It means “Chinese people who have adopted the values of liberalism.” “Libtard” is probably a better translation than “white left.”
The word seems to have gained wide usage first on Zhihu, as some others have pointed out. Zhihu is very much a Quora clone in China, and during the 2016 U.S. presidential race, some Zhihu users answering questions related to Trump and U.S. politics started using the term. For the most part, the so-called baizuo are “hated” by Chinese conservatives really only in the same sense that so-called “social justice warriors” or “libtards” are hated in the U.S. by stridently conservative people: They’re seen as denying supposed biological realities, seen as contemptibly naïve, as slavishly adopting values that sound nice but are thought to be impracticable.