I have seen liberals respond to a hypothetical like this, with a completely straight face, that if some 'expert' said the sky was not blue - perhaps some sky expert or a colour expert, whatever those are - then they would accept that it is not blue.

This broken epistemology is at the root of almost all the problems in the world. A sentient person knows that humans have a shared concept of 'blue' which the sky fits easily into, and so any other definition for the colour of the sky, or of colour itself, is not meaningful. But there is a massive cohort of people who are so unthinking, insecure and deferential to authority, that their definition of the most basic things can be changed because 'labcoat shaman said AKSHULLY, so I say akshully too now'.

Practically all 'science'-based policy is worthless because schemers recognised the potential for manipulation. When science is appealed to in politics or the media, it is nothing more than a truth-laundering mechanism any more.