I agree that they tend to box you into your own little echo chamber if you let them, but I am frequently annoyed and even somewhat offended by what people sometimes post on my FB.
Then don't let people post on your FB. Even though the principle is no different then sending you offending letters, on FB I believe you can at least block people from posting on your page.
But in principle: you don't get it, do you? This is not about recognizing that this is a historic picture, this is about the fact that if this was a current newspicture, it would be censored by Facebook. Facebook would ignore it, deny it, say this never happened. And therefore American attacts on Vietnamese villages never happened.
Do you get it now? That is wat censorship does. Any censorship. It rewrites history to suit the storytellers. Facebook / Marc Zuckerberg = Carver Media Group Network / Elliot Carver.