Well, I don't know that I'd jump to any conclusion about what is legal OR ethical...all of that is really up to the courts to decide.
Just because a case is filed, does not mean that the claim is accurate or founded. And, just because someone is defending a claim does not mean he or she did something wrong.
You are absolutely right...that is for the courts to decide.
If it IS illegal, it will also be unethical to have acted in the way that they did...BUT if it is found to be legal, then they have every right to conduct their business, and it would also be ethical to use good business judgment...so it is all linked...and until the courts decide, we are left to speculate.
The one thing I learned in law school, and I learned it well, is that you can make a good case for both sides and you can argue both sides. A good attorney will be an advocate for their client...and then it is up to the attorney to support their claim with evidence sufficient to convince the court or the jury that their position is right...still, even once decided, many cases are overturned by a higher court...it all hinges on the persuasiveness of the case and evidence presented...not on the claims made by either side.
It will be interesting to watch this unfold...but the fact that the court has not yet issued an injunction against PID, leaves room to wonder why...(an injunction is an order to stop someone from acting and further inflicting "harm" to the other party...and usually a temporary injunction is granted, if warranted, pending a hearing on the matter of a permanent injunction.)