Theoretically, you are correct when you say that "we" should ingnore those inflamatory posts and perhaps the poster will go away.

I think that is the correct approach to take; EXCEPT when YOU are the personal subject of such pronouncements..., then it's a very difficult task to simply ignore. It sounds like good advise to ignore when someone else is being assailed. However, there comes a time when one must stand up and defend themselves against unwarrented assaults upon their character and/or integrity. To ignore such personal attacks sometimes incorrectly conveys acceptance of what the poster is charging as truth, when quite often the opposite is the truth.