If an opponent has my {sensei's divining top} and I {naturalize} it in response they activate the second ability in the top would that cause it to end up on my library and the {naturalize} to fizz out do to no legal target?
Exactly. They draw a card, returning your top to the top of your library, and your natralize fizzles.
But someone can naturalize a top in response to the tops tap ability.