If any civil lawyers are on here, please correct me if I am not completely accurate. The simple answer is this: Slander / libel has to show that someone lost money because of allegations that the speaker or (in this case) writer knows, or should have known was false.
If the defendants believed (based on facts ie... bad air) than free speech can be a defense. To say things to hurt someone in order to cause them, or the result causes them, to lose money knowing it to be false, then you have a case.
This is being adjudicated in a US court under US rules. The defendants will have to answer and the answer (written) will say alot as to where this case will go. There may be non-binding mediation in the begining as well as depositions which are great fishing expeditions for lawyers. If it ever goes to trial, who ever makes the best case usually wins.........right and wrong are not a factor.
I am not an attorney, but have been in civil and criminal courts for 18 years as well as attending schools and classes having to do with civil tort. The big things is this..............attorney's work for money. If there is no real value (people with big money) there will not be much to it when it is said and done.
It will cost the plaintiff a lot if this suit is not settled out of court. The cost of attorney's fees, filing fees, accomodations, food, flights, etc...........may exceed the value of the case and finding an attorney to take it (who is schooled in US law and courts) will be tough. From what I have read (in the filed papers) this one will be interesting but I don't think it will make it to a trial.