...Maybe WS reconcile this with themselves by deciding ahead of time that they never really liked those people anyway and are not bothered by what the loved ones of their BS think of them. Just a thought...
This is likely true. This "Truth-Shifting" occurs in regard to other perspectives, too: the unfaithful spouse's memory of marriage history, their measure of past love for the betrayed spouse, the intensity of past problems faced, the length and depth of their dissatisfaction, etc. And knowing what will be the likely reaction of friends and family can lead them establish relationship buffers ahead of time so that their pain is minimized.
It's sad, but common. And the unfaithful spouse is often unaware of how actively they are involved in making these shifts.