Earlier quoted context omitted.
>the only major cryto with the property of fungibility Yes agreed. Both Bitcoins and ETH tokens can be "tainted" and that taint takes for ever to "diffuse" in the chain. This makes some Bitcoins/ETH less valuable than others. For example, most valuable Bitcoins are newly mined coins (they have no history), whereas a - say - Bifinex hacked Bitcoin carries a pungent smell.
Remember when we called laundering money that because laundromats were used? Just tumble your coins! https://en.wikipedia.org/wiki/Cryptocurrency_tumbler
Much easier said than done:
- it costs money
- most tumblers aren't safe at all (who's to say they aren't operated by the govt or that they don't keep logs)
- in some cases, you might not get your coins back at all
Coinjoin for BTC is a better approach, but it's also far from easy to use (need a special wallet) and is basically useless until it sees mass adoption.