I think the RF will have to respond, in some way, sooner or later, to be honest.
The book has shot to the top of the Amazon best seller list, and with purchases and prior orders, it's rocketing up the lists of retail bookshops. So, a lot of people will read it, and a certain proportion, especially across the pond, will believe it all.
Which doesn't do much for their reputations.
From purely personal and recent experience, I found that the less I responded to public allegations and accusations, both verbally to others, and spread all over various social media, (naming me), which were all untrue, the more extreme my accuser got. Keeping a so called "dignified silence" didn't work at all well.
In the end, it required, and got, a robust response, both personally and using a solicitor.
Sitting silent and just taking all the brickbats isn't always the answer.
However, the RF will, rightly, do what they think is the best way.😗