ummm... i think the Silbury vandals are pretty reprehensible. But i feel you need to tread carefully when complaining to a bookstore about the content of the books they sell. I'm not sure suppressing books is a healthy thing to do - whatever you feel about the content.
There is a whole slew of books, for example, which make claims about the relative IQs of different races (almost always as an attempt to "scientifically prove" white folks are more intelligent). I utterly despise this attempted co-opting of 'the scientific method' to make unsustainable racist points. But i will (however much i hate having to do it) defend their right to publish their opinions. To do otherwise is to begin down the road that leads to book burning and fatwahs against writers.
If the Silbury vandals broke the law in doing what they did (i have no idea whether they did or not - i'm not familiar with the details), then they should be held to account for that. And there's no question that their actions were ethically unsound and should be exposed as such and denounced. But that's a world away from advocating the suppression of books. And it sets a *really* dangerous precedent when you start insisting that book sellers are responsible for the content of the literature i am allowed to access.
Do you really want the CEO of Amazon, or WH Smiths, or Barnes & Noble to be deciding which books are "acceptable" and which ones aren't? Cos actually, that's a decision i'd like to make for myself.