What they don't see, in my opinion, is that it is their very dread at such a possibility that is really what is keeping them from doing those things.

Why do they have that dread?

A common trope is "my momma raised me better than that." What if momma has low expectations? That banks on all of morality being inborn instead of inculcated, which strikes me as a terrible bet.

Also, it's easy to see cases where we cringe at things indirectly. I might not cringe at the thought of cheating on my spouse, but cringe at the thought of social rebuke. If society changes its incentives, then I will change my behavior. In this hypothetical, I need you to keep me honest; if you stop caring about the state of my marriage, then so would I.

(Indeed, that's the primary reason I go to LW meetups and such; in order to get a social group who gives me the incentives I want to have.)