Why would an absurd idea stick around? They tend to because our brains like to generalize and we like to feel like we are a part of a tribe.
Generalization (treated a synonym to simplification last week) is valued by our brains because it makes life a lot easier for us! Almost all animals display this trait because it is essential to survival. If you hear a rustling in the grass, it’d be maladaptive to always wonder what it is or must find out. Thus only a few cases are enough for us to understand that the rustling is a threat. Over thousands of years of evolution, our brains have been built around this concept. Thus, generalized ideas stick in our head better than complicated or nuanced ones. Relatedly, they also spread more easily.
Our brains will try to make sense of absurdity, even something as absurd as this!
Our tribal nature is similarly based in evolution. In the age of early humans, the largest risk that one could face was being ostracized from one’s tribe. Thus, we evolved to be cooperative with the people we associate with and to seek their approval.
Humans today will have multiple tribes: a family, a church, a company, a community, a country, as well as political and socioeconomic tribes. As several of those tribes have weakened on average (church, family, and community), the sway of political tribes has risen and for more and more people serves as the main tribe they associate with.
That shift toward ideological tribes poses many risks. Most notably, it increases the cost of deviating from a tribe’s orthodoxy. Because each tribe has already been ‘infected’ by easily-spread-but-absurd generalizations, we end up with entrenched absurdity in our political discourse.
So our brains simplify ideas. We compress them, and share them (as memes). Along the way, we gather and remember anecdotes where our simple ideas were good and why competing ideas are bad (this is called confirmation bias: a well-documented phenomena for another time). These ideas grant us membership into our tribes, whether those tribes are religious, political, or cultural.
The above path happens irrespective of how good an idea is, or how accurately it has generalized our complex society. Naturally then, we end up with good and bad generalizations acting to shape society. A basic example of a good generalization would be “gravity pulls you down” - it’s not strictly true in every case, yet it proves quite useful at preventing people from falling off large cliffs.
Yet plenty of awful ideas have been broadly accepted at one point in time. Distantly, we can look in shock now at how Romans felt great about throwing gladiators into death matches as spectator sport, or how slavery was rampant all across the world. More recently, you could look at the mania that swept through Cambodia during their genocide.
Those ideas all feel, well, absurd (or evil) to us today. But they were mainstream at one point, accepted by millions. Plenty of less-deadly-but-still-absurd ideas are still floating around society today, they are just harder to spot because many people believe them.
To close succinctly: ideas are simplified and spread with little regard to how accurately they reflect our complex world. Thus a functioning society needs a mechanism to weed out the bad ideas that percolate up so that the good ones can flourish. But that’ll have to be a story for another time!