I would not respond, at least for the time being. The kind of people who are making assumptions and making comments knowing that it hurts the family, aren't going to change because of any reply you make. Arguing with them only encourages them to drag out the venting.
The problem with most of this is the anonymity, and even if names are given, the physical distance. People will say things that they would never have the guts to say to someone's face.