Can the Supreme Court ruling in the Facebook free speech decision be used to argue against the granting of an OP in Illinois

Your question is not a question which is easily answered by any except the Courts themselves.  However, I will try to take a shot at it because it is an interesting question. The Supreme Court case is called Elonis v. United States.  The Court held that a "threat", in the criminal law context, cannot be merely based in the "reasonable person" standard.  That is because criminal law requires something called "Mens Rea", otherwise known as a "guilty mind".   In order to act criminally, one must (almost) always act with a culpable mental state, be it recklessly, knowingly, or intentionally. However, an order of protection hearing is civil in nature.  There is no requirement of "Mens Rea" in civil law.  Indeed, the "reasonable person" standard is a familiar concept in any areas of civil law. The vast majority of negligence torts committed in the United States are based in the reasonable person standard. In civil law, "negligence" is actionable. That is what I personally believe is the distinguishing fact between Elonis and a challenge at an order of protection.  Elonis was a case which was criminal in nature that required mens rea.  An order of protection is a civil pleading which does not require mens rea.  Of course, this is my own personal opinion and is not to be considered legal advice.  I suspect nobody will be able to say with certainty what the answer is to your question until your question is answered by the Courts.