This:
If the idea is that there is some content you don't want a subset of people to see than it's a mistake to post it.
is a privileged perspective.
I'm guessing a lot of HNers aren't subject to gang injunctions, but imagine for a moment that you are. Suddenly, "pictures of me and my friends hanging out" become dangerous, something that can land you in jail.
Or let's say you identify as queer to your close friends and immediate family, but you have more distant relatives who you're not ready to tell just yet, but don't want to 'unfriend' on Facebook.
Or let's say you're a member of a religious group that's persecuted in the country you live in, but you'd still like to be a part of Facebook groups full of people for whom it's not an issue.
The fact that you're able to be the same person in public at all times is a privilege that not everyone has. For everyone else, you're saying that constant self-censorship should be "good enough". I find that perspective abhorrent.