Can I sever Ties With My Selfish Sister?

It has been curious, amid the pandemic, to see normally law-abiding people exempt themselves from laws because they don’t agree with their rationale. Even if you thought (against all the evidence) that vaccines do no good, you wouldn’t be entitled to second-guess the judgment of political officials who have taken expert advice and made rules. Pandemic scofflaws like this man are making decisions for other people — people who might not have chosen, say, to consort with the unvaccinated.
As we look forward to a post-pandemic (if not post-Covid) era, maintaining your other friendships should get easier. In the meantime, I see no reason not to let this man know where you stand. As the social psychologist Tom R. Tyler argued in a classic study, norms of legitimacy, more than fear of punishment, explain why people obey the law. By sounding off, you’ll be helping to sustain those norms.
What has protected us here is the whole scheme: vaccinations, certificates and so on. Any individual defection isn’t likely to cause a great deal of immediate harm. The main wrong he’s doing is displaying an egocentric contempt for all those who have troubled themselves to support the scheme by putting in the small contributions that make society work.
My spouse and I are fully boosted seniors. I am currently cautious in all things, having a compromised immune system. After the holidays, we agreed to indoor restaurant dining with friends who had just returned from a family visit to the Midwest.
As we were leaving the restaurant, the wife mentioned that she had a forged Covid-19 vaccination card. She said that she had Covid early in 2021, has antibodies, tests herself and never got vaccinated. When my spouse questioned her husband privately about this, the husband backpedaled, claiming that she didn’t have a forged Covid vaccination card (which could be a felony) but that restaurants don’t always check for cards.
This was the third time we have met these folks for dinner in recent months, arriving separately and always at a restaurant with indoor dining only. Our cards were invariably checked upon arrival. Their stories just don’t jibe. I am beside myself with disappointment at the blatant dishonesty. More important, I am conflicted having this knowledge and keeping it to myself, since we know many of the same people. Name Withheld