No, their complaints aren't private...because they post them immediately to Facebook, snapchat them to someone else, or can't help but tweet their latest crisis to their 465 followers. Surprise, announcing your private thoughts and feelings to hundreds if not thousands makes it unlikely your thought is "private".
You do realize this is about surveillance, right? Even if you have nothing to do with Facebook, your communications are still being monitored.
They can have "private thoughts".
Oh, that's nice.
There are even lots of opportunities for actual privacy
And thanks to modern technology and governments that are willing to use said technology to infringe upon people's rights, the number of such opportunities is decreasing.
(unless you choose to avail yourself of modern communications).
Well, that's kind of the problem, isn't it? This is the information age, and I don't exactly expect people to abandon modern communications just so they can ensure that their corrupt governments aren't spying on those sorts of communications.