What about what libraries do in general. By buying some number of copies and then letting many people read those copies, it leads to fewer people buying books overall leading to less pay, meaning those who depend upon income from writing books to be less able to afford continuing to write books.

And any arguments along the lines that libraries actually lead to increased numbers of readers and thus overall increase book sales could also apply to this instance as well (I've even seen such arguments made about piracy in general, though I've never seen any conclusive research indicating if the argument is realistic or not).