Shows/concerts cancelled? Without a Twitter mob?! Inconceivable!
It's much easier for protestors to have success stopping/preventing specific
events. That event is going to happen in one specified place. All resistance can be focused on (or at) that venue to make fighting the pressure more trouble than it's worth.
A book makes its appearance simultaneously at thousands (or millions if you count ebook readers purchasing books from the comfort of their own recliner) of locations at once. Protesters pitching a fit in one corner of social media don't have a snowball's chance of stopping a book that's already on a publisher's release calendar--and if advanced copies are already circulating. There's no target or venue where protest can be adequately focused. The book release will come and go and most fans/consumers will never even be aware there was ever a problem.
One has to seek out this kind of pre-book-release news to even know it's going on. And most people are already well-aware that online book reviews need to be passed through a personal relevance filter of some kind anyway.