Same principle, really. In geopolitics if you either go to war or you decide to do some empire building if you want things to remain stable after you turn your back you end up being responsible for the aftermath. And if things go pear shaped and you turn your back they likely will come to haunt you in one way or another. These are not laws, merely extracts from observable reality, from Roman times right up to the present.
Sure it could end different but for some reason it never does.
You are suggesting that westerners should, of their own accord, import millions of fighting age and potentially bitter men into their homelands. You admit this is a 'bit of a problem' for those westerners. Now you are suggesting that if westerners choose not to import these millions of people into their homelands, some nebulous force will haunt them. And your basis for this claim is, ultimately, the fact that civilizations tend to fall apart after a while? Given the enormous complexity of the causes of the downfall of great civilizations, do you realize how absurd that sounds? Given the enormous, albeit temporary (as all things are), success of civilizations that didn't feel bad about taking advantage of their neighbors, do you understand why your argument is so unpersuasive?