If you really weren't "trashing other online" but telling facts without calling anyone names, as you say, I personally can't see any reason to worry. I'm no legal expert, but I'm fairly sure that it is illegal to fire an employee without a good reason. If you were fired over this, you could sue - and no sane boss would risk getting sued for firing somebody because of a harmless facebook post. So unless you already have to worry about your job for other reasons or you actually harassed somebody, keep calm and stay factual. Depending on what the relationship with your boss is like and whether your boss is fat or not, it might be a good idea to tell them that somebody on facebook is harassing you and threatening you and your job over a neutral, informing comment on facebook.