Imagine you owned a library. That library is in principle open, anyone can go in and read books, browse the web, wank in the toilets, etc. It’s a good place and it takes you some doing to keep it so.

Now imagine a bus full of book-hating pyromaniacs parks outside (in this metaphor, there is such a thing as book-specific pyromaniacs, just for the sake of illustration).

Surely you’d hang up a “no pyromaniacs” sign?