Earlier quoted context omitted.
That age old "I have nothing to hide" argument. AKA "they're nice people, what could go wrong". This is not the point. The point is: Information in the wrong hands can become dangerous , period. People change. Companies change. You have no guarantee Facebook will preserve the vision they have right now. You have no guarantee their new CEO won't have a different opinion... (wont be a "Trump"). Also you have to realize…
Not OP but even if the next Hitler would get all my Facebook data I still don't care personally. Am I naive? I do understand why people have a problem with it though.
Do you have Jewish ancestry?
Of course the next "Hitler" probably won't be after Jews. Next time it would be Muslims or immigrants or Stalinist purges of anyone who disagrees with the administration.
You don't know today what opinions would get you put on a list tomorrow.
And if you've never said anything that anyone could ever find objectionable, you're probably doing something wrong.