There is an objective truth, but many people know it by the alternative name "left-wing bias". You see the problem? (Or, if you prefer, pretend I wrote "right-wing bias")
Flat earth may be a better example, since everyone HN user is hopefully a round-earther. Suppose you are talking to someone who thinks the earth is flat. Flat-earth belief used to be a joke, one or two decades ago, but now these debates actually happen with some regularity and the round-earther never wins. Do you think you could do better than every other round-earther? The proverb about playing chess with a pigeon is relevant here. What you call "objective reality", they all "round-earth bias".
Flat earth may be a better example, since everyone HN user is hopefully a round-earther. Suppose you are talking to someone who thinks the earth is flat. Flat-earth belief used to be a joke, one or two decades ago, but now these debates actually happen with some regularity and the round-earther never wins. Do you think you could do better than every other round-earther? The proverb about playing chess with a pigeon is relevant here. What you call "objective reality", they all "round-earth bias".