Imagine that we have a conversation and I say to you, "I believe in the gerflagenflopple. You cant prove that the gerflagenflopple does not exist, therefore it exists." You can see that this is ridiculous. Just because I have invented something out of thin air doesn't mean that its non-existence is suddenly unprovable. There has to be evidence that the gerflagenflopple exists to assert its existence. Since there isn't, it's easy to say that the gerflagenflopple is fake.