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.
To protect the treats
I'm not kidding at all
The open embrace of imperial violence to maintain one's own personal lifestyle will be an increasingly popular position as material conditions deteriorate: Treatlerism
I'd argue this is the third tenet of the evergreen "life, liberty, and 'the pursuit of happiness'"
The pursuit of my happiness even at the cost of your life and liberty