Certainly there are events which are beyond human intervention, but that's the way the universe goes. In the real world, if such a thing happens, we're screwed, no doubt. But it hasn't happened and it's dubious what the odds are of it ever happening.
In Luthor's worldview humans should be uniting against such a threat, with a genius such as himself in charge, and with the tech he can devise, it's a distinct probablity he would win.
Plus, even on a much smaller scale, call it dependency or whatever, but if I were assaulted by a criminal I'd be damn grateful to any superhero who could give me a hand, I certainly wouldn't think "hell, no, why couldn't a human cop save me!?"
But you probably should be thinking about that, because it reflects a possible underlying problem with the society you are living in, that you actually DID require a hero to save you because he happened to be passing/on a whim, as opposed to a properly funded and organised police force capable of dealing with the assault on you.