Are you a lawyer? Because if you are, you should turn in your bar card. You don't have to show 'just cause' to file a complaint. You can file a complaint for anything - including suing the Pope for bastardy. There is no provision in any state code or federal code for showing cause before you file a lawsuit - unless you've been determined to be a vexatious litigant, which is a very narrow exception.
Well, that may be how you guys handle it in liberal states, however, where I live, where we still have constitutional conservative judges, one must first establish ‘jurisdiction’ and then once that is established, one must establish ‘just cause’ in their brief that actual ‘harm’ may have been done. The other side files their brief and then the judge determines whether or not to take the case. And it does not take a mountain of money to do that.
So as I said, if one stick to facts, undisputable facts, they have nothing to worry about should they decide to write a book about the facts in front of them.