No one claimed that the universe was not created ex nihilo, so no one needs to prove it. I would claim that I am unaware of any scientific evidence that indicates that it was 'created' or 'came from nothing'. That would be sufficient reason not to believe the universe was created ex nihilo. No logical proof required, though some people claim that something can't come from nothing; they seem to be in the same camp that claims God did exactly that.
I'm not anti-Christian. I'm anti-stupid.