It doesn't, obviously, since it's not possible to prove a negative. Much like there's nothing that proves that you won't begin to be able to fly if you stand on one leg long enough.
If what you've been shown so far is insufficient evidence for you, then I'm afraid you're on your own. I don't need to play the "how about this" moving goalpost game.
How do you know that exposure to comments by people named “cwillu” does not lead to cancer by some delayed chain reaction that takes decades to become visible?
e.g. There could be some effect via a delayed chain reaction process that takes decade to accumulate to be noticeable...