Paul, just a thought from a complete outsider.
If public opinion in the forums and on the 43,271 different Facebook groups is anything to go by, all this kerfuffle is leaning toward the general opinion of "Raymaekers is doing the right thing, ANDI are being a bunch of muppets."
As you say, the people being hurt are the ANDI rEvo instructors - but any legal action you might pursue won't help them, they are stuck with either leaving ANDI or leaving rEvo.
Dropping down to some other peoples' level of calling in the lawyers (the civilised equivalent of monkeys flinging poo about the place) could do a lot more damage to your reputation than just ignoring the annoying little dog that barks at you from the neighbour's back yard.