I’d like to think your core argument is correct, and that people could be swayed by empathy and appeals to some basic commonality. Unfortunately two years spent interacting with Trump supporters across the USA left me absolutely certain that there is no effective strategy available. There are simply some categories of problem for which no solution is possible.
In physics, for example, we can’t travel to the nearest stars at a speed faster than light no matter how much we wish we could. Once a star burns through its material, that’s it. There’s no solution to the problem of how to get the star back to its original mostly-hydrogen state. With slavery there was no meet-in-the-middle compromise: one either abolished slavery or one tolerated it; there was no de Broglie superposition of all possible states simultaneously.
The harsh reality is that a great many people are, sadly, very stupid and very ignorant. The trick isn’t to hope they can develop more adequate cognitive function nor to hope that they can somehow learn basic human values. They already believe they possess these traits. The way forward is to recognize that a great many people will simply believe whatever they are told; therefore the solution to today’s problems is to tell them more adequate things. People need better stories.
These stories need to be very simple, because complexity will be beyond the grasp of far too many. The stories need to be oriented towards humane behaviors, because “monkey see, monkey do.” And the stories absolutely must not include infantile nonsense about gods and goblins because that’s a one-way road to intolerance and hopelessly incompetent thinking.
There’s no way the USA can get there. But perhaps some other country, many years from now, wishing to avoid the kinds of self-harm we’re seeing around the world as mindless populism takes hold, will make an attempt.
We have to hope.