Your premise is a little self-referential. Civilizations imply civilized, ours and theirs are both going to think themselves civilized, but might not recognise

Your premise is a little self-referential. Civilizations imply civilized, ours and theirs are both going to think themselves civilized, but might not recognise one another as such. Aboriginal Australians didn't find the colonisers of that continent particularly civilised and the colonisers didn't find them civilised. Our planet could be seen as so uncivilised as to be a worthy candidate for annihilation. Or building a space bypass through our solar system.