So far historically it was "they're not Christians", then it was "wrong location" (cause they wanted the land/resources), then it was "they're not the right race", then it was "wrong economic system", and now it's "wrong culture"; what's next do you think?
EDIT: By justifiable I don't mean it's actually justifiable, I mean most people will consider it justifiable.
"They make the nation weak" will be for targeting internal minorities, and we'll use the regular "sorry, wrong race" when fighting Russia and China. In other words, same as always.