Quite the opposite. If a 'loving heavenly father' who 'so loved the world' allowed a nuclear holocaust to occur, it would only prove one thing: that he doesn't exist!
In fact, this has effectively already happened with the atomic bombs dropped on Hiroshima. If God wouldn't intervene to stop that (and countless other genocidal events in history) then why the f*ck do Christians believe he will ever intervene for anything?
The evidence is unmistakable. The Biblical God simply doesn't exist. And if we are the progeny of something higher than ourselves, whether alien or whatever, it clearly has about as much interest in us as we do in a termite nest in the Sahara.