I commend that you are so concerned with your uncle; however, I am not sure of all that you can do as far as his posts are concerned. You could discuss this with your parents and possibly your uncle. Perhaps if you or another family member he feels close with talks to him, you might be able to reason. Also, you can block people on Facebook, which might be something you can look into. It sounds like he is going through quite a difficult time, so offering support is very beneficial. You could even suggest that he seek counseling services in order to resolve some of his issues. Good luck with everything, and please keep us informed.