It might not be true, but remember, absence of evidence is not evidence of absence and this is a case where risk really is unbounded, so you better be cautious.
Man, I really wish people would stop saying this. It's just completely false. It's a basic result of probability theory that if A is evidence of B, ¬A is evidence of ¬B.
The trick is that the strength of the evidence is not equivalent. It is not correct to say "Evidence of strong evidence is strong evidence of absence". More generally, A is strong evidence of B does not imply that ¬A is strong evidence of ¬B.
We have an absence of evidence for æther, but we are pretty certain that if it exists, we would have evidence of it. Our confidence of that is strong enough to state with some confidence that æther does not exist. For practical intents and purposes, we can say that the absence of evidence of æther is evidence that it does not exist.
Not all absences of evidence are made equal, some are more significant than others.
Otherwise all crypto projects are off limits, including Tor and Bitcoin