Q : So these beings cannot be killed? Not even by an outward circumstance having nothing to do with being violent with each other? Like a Black Hole (just to make something up here) swallowing their civilization’s home?
A : There is no outward circumstance within the physical universe that could cause them to equate the changing of their manifested form to losing their life or ending their existence
Q : When you do not fear losing your life, ever, you have no reason to ever become violent? What about losing something, or not being able to get something, you desire?
A : You have already been told, by masters on your planet, that desire that you feel must be satiated is the cause of all suffering. And suffering is the cause of all violence. Eliminate suffering and violence goes away, evaporates, dissolves, disappears.