First, I want to establish a few things. I’ve addressed ownership in the past. Once something in the hotel room is in one’s possession, there is a shift in who has a right to it. However, implicit and explicit agreements have been made, limiting the transfer of stewardship. For instance, there is an agreement that the person staying in the hotel room will not take the TV with them.
In the same way, the bibles that are left in the room are intended for a specific function. That function is “reading” and “learning” about the religion discussed in the book. Those terms are clear, even if not stated explicitly. It is a tacit agreement. One could argue that there was no such agreement, and no stipulations of use were made, but then, it could be argued that the bibles were not meant to be taken at all. The bibles are not listed as free to take. It is implied. There is no vagueness to the intended use of the book, and if one takes the book for a different function, then that person is not upholding the transfer agreement. Since the person does not have stewardship over the book, unless the transfer agreement is upheld, the act of defacing or destroying the book is vandalism.
In gift law there, there is a concept known as a “conditional gift.” It is recognized that certain conditions can be placed on a gift, and that if those conditions are not met, the gift can be revoked and reclaimed. The condition cannot something dependent on the will of the donor however (uslegal.com).
As another example, consider a person who is giving cups of water out to people in the heat. Is it clear what the intended use of the water is? It would be hard to argue that anyone walking by wouldn’t be aware of the water’s intended use. Therefore, if I took one of the cups, and dumped it, or used it to wash my shoe, I would be using the water improperly. While the monetary damages would be minor, it would still be destruction of property.
Furthermore, society does not only look at individual damages when determining appropriate behavior, but also at cumulative damages. Certainly if I’m the only one dumping the water, not much harm would be done. But if a few dozen others started doing the same, pretty soon there would be no water left for those who need it, and the one giving away the water would be losing significant resources.
The same is true in the case of the bible. Even though one bible isn’t that expensive, if people started using the bibles with the intent of defacing them or destroying them, it would cause a significant amount of financial damages to the group that is giving them away. So, while defacing a hotel bible may seem like a fun idea, it is indeed vandalism, and it is not acceptable.