You don't seem to understand that it's not an actual, wholesome worldview, but just a bunch parts of different (often contradictory) worldviews that are applied arbitrarily, when it benefits the left.
Leftists will not dispute a rock is a rock up until it seems advantageous to them. Then they will claim that it is merely your perception of it being a rock on a hill, and that what they're seeing is a gray spongecake. If you then go and pick up the rock, noting that it's nothing like a sponge cake, they will claim that it is merely a very old, hardened sponge cake covered by dirt. When you actually cut it open, they will claim that they have indeed been correct, since when they said "sponge cake", they meant an object that you know under the word "rock". Since all words have been assigned to objects by men, and language is subject to change, and words can have numerous meanings, they will state that their subjective interpretation of the word "sponge cake" led them to call the rock as such, and that it's your own fault for not defining what you mean by "rock" at the very beginning. They will accompany it with a media campaign painting the usage of the word "rock" as deeply offensive, and pushing "sponge cake" as the only polite and politically correct way to describe a rock. After they're done, when half the population won't ever dare utter the word "rock" as it will have lost its original meaning and only be known as a slur, and when they will only call a rock a "sponge cake", they will point back to the original argument, and say that clearly, you have been in the wrong, since you claimed that it was an indisputable, objective reality that the object on the hill was a rock, when it was, actually, a sponge cake.