Thus, other adaptations, e.g., the desire to avoid social shaming, can be used to contract them.

It's an interesting thought. How would you control for the baseline levels of social shame that racial minorities, poor people, and teen mothers are already subjected to?

Compare the situation today with the situation 60 years ago. Notice what is and isn't different.

All sorts of things. There's a lot less lead paint on the walls, for instance; a lot more black men in prison for victimless crimes, too; "the situation" is hardly simple. What leads you to single out your particular claim?

So you agree that "stigma and fear" is in fact an effective way to change people's behavior.

Running a power drill through the eyeballs of people you dislike might "change people's behavior" too, but that doesn't make it a policy proposal rather than a psychopathy symptom.

In other words, it isn't clear that this is the same sort of thing at all. And specifically, the reasons certain proposals wouldn't work have to do with political realities — e.g. if you try to generate "stigma and fear" by forbidding doctors from treating teen mothers, the doctors are not likely to cooperate.