Some of our judgments are unstable, in the sense that they are an artifact of, or endogenous to, what else we see. This is true of sensory perception: Whether an object counts as blue or purple depends on what other objects surround it. It is also true for ethical judgments: Whether conduct counts as unethical depends on what other conduct is on people’s viewscreens. It follows that conduct that was formerly seen as ethical may come to seem unethical, as terrible behavior becomes less common, and also that conduct that was formerly seen as unethical may come to seem ethical, as terrible behavior becomes more common. In these circumstances, law (and enforcement practices) can have an important signaling effect, giving people a sense of what is normal and what is not. There is an important supplemental point: Once conduct comes to be seen as part of an unacceptable category – abusiveness, racism, lack of patriotism, microaggression, sexual harassment – real or apparent exemplars that are not so egregious, or perhaps not objectionable at all, might be taken as egregious, because they take on the stigma now associated with the category. Stigmatization by categorization can intensify the process by which formerly unobjectionable behavior becomes regarded as abhorrent.
Sunstein, Cass R, The Power of the Normal (August 21, 2018).