[X] [Reasoning] "I believe that some spirits are righteously angry for crimes committed against them, but they can't all be like that, and not all for the same reason. I believe it's dangerous to assume when there's so much we don't know, and that it's important to show proper respect and reverence to the spirits, but I still have a suspicion that too much has been lost as the ancient legends have been passed down. There could very well be other reasons the spirits do such terrible things, reasons that we have yet to relearn. After all, there are conflicting legends about the spirits and the past, each with at least a kernel of truth."
[X] [Reasoning] The spirits sound like they are acting like hunters without a chief. The hunters will keep hunting even if there's nothing to catch if the chief doesn't tell them to stop and move on, so if these spirits only know how to move bones, then they might move bones even when there is no body around the bones and they keep looking for more bones to move even if they already have enough. Are there spirits inside people too?
[X] [Reasoning] Why would their motivations matter to us? They are as the weather or the animals, dangerous when approached incorrectly, harmless when approached correctly and maybe useful if one actually knows what he's doing. I can't even say for sure they have reasons as people have, nevermind find out which those are.