Any alien civilization that has mastered the technology of intergalactic space travel would necessarily have the power to turn the earth into a briquet and there is likely little we could do about it. However, consider that if such highly advanced civilizations exist …why the heck would they use that technology to cross intergalactic space just to visit what is to them a very primitive civilization? I suppose we could use the example that our civilization has crossed continents to study what we could see as other primitive civilizations, but, that example doesn’t really compare. The level of advancement needed to cross intergalactic space is so beyond our capability there would be no purpose to expend the resources needed for such travel other than to simply satisfy their intellectual curiosity. Again, why bother?
Because they manage this end of Creation?