The reason what these amazingly benevolent companies are doing and collecting matters is because the systems we build today are precisely what will power the dystopias of tomorrow. As the GP mentioned, Nazi Germany used census data to select and track their victims, aided by some primitive computational technology built for the Nazis by IBM. In spite of how primitive all of this technology was, it ended up being quite effective at enabling them to achieve their ends.
Now compare this to the systems we're building today. Genuinely bad people do, and will, manage to take power in any system. It's not a question of if, but when. And these systems that we're building will be at their disposal. It's the same reason that in politics if you're considering granting the government more power you shouldn't think about today, but about tomorrow. Not do I want "this" administration to have those powers, but do I want future administrations - whom I will vehemently disagree with, to have those powers?