Yeah it's nothing you can do, because even outside of tibia they can ping us and it's not your problem. But using this method to their advantage of war etc.? I think it's being taken too lightly.
Seeing as we advice you to both contact your ISP and to file a police report (if you know who it is that is doing it), I wouldn't say that we are taking it lightly. However, we can't do this for you and we can't force you to do it - people being "pinged" have to take actions themselves, we can't do it for them, the only thing we can do is to share our advises on how to handle the situation and how to prevent it from happening again.