You can't have it both ways. End to end encryption or open groups with censorship by moderation, pick one. This is a side effect of private clubs and private online communities. While I don't condone the behavior, we need to get more creative on how to police this than putting in place mechanisms for violating everyone's privacy, which is just lazy and dangerous.
It's hard to read some of these stories without ignoring the current surge of schadenfreude that writers are capitalizing on.