And even if they don't want to sell Amazon's books, publicly announcing that fact seems unlikely to achieve anything.
I'm not saying it's the right decision, but it does have a strategy behind it.
On the other hand, their leverage is probably greater with ordinary books (as compared to comics). I presume they have a bigger slice of the book market and it wouldn't surprise me to find out that browsing-based sales are more important for books than comics.
I'd also say that the customer experience isn't as bad as it sounds. B&N will still special order the book for you and it will be sold at bn.com. With the exception of books by bestselling authors that B&N "should" have, I suspect most people aren't going to realize B&N has refused to stock the book. Instead, they're going to think that the particular B&N they're in doesn't happen to have a copy.
While it might be somewhat of a big deal for the authors involved, it probably won't be much of an issue for anyone else.
Seems like an appropriate response to me.