Actually, the proper method would be to assume that no entity exists unless there is evidence that it does, in fact exist.
One of the rules of logic is that you cannot prove a negative. You can observe that there are no unicorns or fire-breathing dragons. but you cannot prove that they never have existed. you were to find some strange fossils, perhaps you could prove that they once existed.
The absence of Ice Giants is most likely due to the fact that there never were any Ice Giants in the first place.
The burden of proof for God's existence, like the burden of proof for the existence of unicorns, fire-breathing dragons, and even the Flying Spaghetti Monster, rests upon the believers to prove.
Jesus, it appears, has yet to abolish wicked people. He should, at the very least, tell his Daddy to stop making them. They are, after all, mortal.