Trading in cryptoCurrency is about as unethical as buying a bottle of water given how criminals also drink water. Do you have a problem with using money? Criminals use that too.
What about guns? I think you already know.
“Using (something) because it’s used by criminals” is a cop-out argument. It’s a strawman and a red-herring fallacy. It’s non-sense.
Of course, it’s ethical to use CryptoCurrency!