I think the argument is that "good faith" necessarily doesn't hold when you allow one group of people to post threats, harassing content, and misinformation while you ban another group from doing the same thing. In other words, selective enforcement to favor your friends doesn't seem to be particularly good faith. I'll leave you to decide which platforms to investigate and to find selective enforcement: all of them do it.

To be clear, I don't agree with those interpretations of section 230 - and neither do many judges.