HOn, you really have right on your side. Such people need to be confronted, and it is brave and strong for you to do it. People can have whatever feelings they want, but there are appropriate ways and places to express them and Facebook and the Coffe room are not them. If I need to vent on a colleague, I make sure it is not at work and between two pairs of eyes that i know will just let me vent and won't take it further.
It sounds good that you have the supprot you do from your manager. Huggs, and Goodluck. Imagine us being in your backpocket when you take on the "#¤%es"