We, on the left, are “The People of the Theory” (just as Muslims, Christians and Jews used to be known as “The People of the Book.”) We like to formulate our own moral-political philosophies, theorising on how human society and psychology operate.
I think this is why left-wing politics is so often associated with younger demographics. Younger people are still exploring their world, working out its social systems and procedures, its political and ideological structures.
Ironically, this is a natural extension of how the human brain learns and develops. A baby experiences a physical phenomenon, a child or an adult encounters a plausible idea or fact, and we assume this is evidence of a universal truth. Then we generalise and apply this to the whole world. If a toddler falls over and hurts themselves, they conclude that falling is a cause of soreness, and they should be careful not to do it again. If we didn’t do this we would never learn and would constantly make the same errors, ultimately compromising our chances of survival. Generalisation and assumption are vital and necessary parts of cognition.
It is a wise cognitive strategy, but all human mental processes are fallible. It is inevitable, then, that we will frequently overgeneralise and make prejudicial assumptions. In English language acquisition, children always go through a stage when they over-generalise the regular form of the past tense, once they have learnt it (“-ed”), so they say “he go-ed” and “we sleep-ed”.
In adults, the same cognitive process is in operation when we are cut up while driving in France and conclude that “The French are terrible drivers” or have an argumentative male colleague, and so decide “men are more aggressive than women” or encounter complacent and thoughtless entitlement among some feminists who are white, and thus believe “White feminism betrays women of colour”: you identify a type or class (of person, in this case) outside yourself and then attribute one characteristic of one member of the type to all its members.
The difference between children and adults is that child learners keep learning and so self-correct, whereas older people often stick doggedly to their over-generalised assumptions and prejudices, and even reinforce them in each other, if they help to cement tribal unity. Our minds are already less plastic and flexible, even by our twenties. Old Lefties like me and Jeremy Corbyn aren’t principled, we are just stuck in our ways, our atrophied brains rigid as arthritic claws.