https://www.havenandhearth.com/forum/viewtopic.php?f=40&t=69589
Not a bug, but an intended feature which is fully accepted and behavior that seems to be supported by developers of this game.
Many players have complained of his actions, but devs don't care. Better quit the game now before you have anything more to lose, because you have no way of defending from him and he will destroy it all with his bots etc.