I don't think we can have much of a conversation here. I simply believe that foreign nationals shouldn't take out ads to influence the elections of countries in which they're not a citizen. If we can't agree on this, then we'll just have to agree to disagree. And, just in case anyone tries to counter with a "pot calling the kettle" argument, I don't care if the US government has ever tried to influence the elections of other countries. I don't think that's ethical either.
So, just to restate my position, if what Facebook meant by upholding the integrity of elections amounted to preventing foreign nationals (non-Germans) from buying political ads on their platform, I'm all for it.