The publisher's problem is that this isn't some nut-job that can just be dismissed out of hand. Dale Askey appears to have the qualifications to know exactly what he's talking about here so they have to try and shut him up. But suing McMaster University over the personal blog of one of their employees personal blog opinions is way beyond reasonable -- although that's probably either were the money is, or that they hope to punish Mr. Askey by getting the university to fire him as him being too much trouble to keep onboard.
Under all circumstances the publisher is wrong here. The proper course of action would have been for them to line up equally (apparently) qualified academicians on their side of the argument and let the book-buying institutions decide for themselves. It would seem that both sides of the argument were already being hashed out on the blog, and now arrives The Streisand Effect in spades!