I’m not a Bitcoin or crypto expert (though I remember news about a decade ago about unrelated data, including pictures, ending up in the ledger. Maybe they fixed it?) Rather I think about what I’d want in a currency that we don’t have in state-backed currencies.
And yes, anonymity of transactions is one of the, money laundering is about justifying gains to a surveillance state on the grounds that only state-approved transactions should be allowed. Like the internet, the economy is and should be bigger than the regional states we have, unless you want Hollywood telling you what content you are allowed to watch and how many times before your license expires.
One of the problems with state-proprietary banking systems is that they can be manipulated for political purposes. It’s nice when this means depriving dicks of their money (say Putin and Russian Oligarchs) but it’s not very nice when it’s used to silence journalists who embarrass the ownership class (e.g. Wikileaks) or is used by industrialists to block competition (e.g. the MPAA and RIAA arranging for the freezing of Kim Dotcom’s assets, and those of Megaupload, which was about to release a new music distribution system).
The point is to create a currency that states cannot control or regulate.
Yes, there are matters like the black market. CSAM transactions have become more difficult to trace while cryptocurrencies are stable, but I suspect these can be addressed piecemeal when we actually confront problems like drug abuse and porn production. As it is, the people who do the most damage, cause the most cost and death have enough influence on state regulators of currency so as to not need to launder money. (Though they may fold conflict diamonds into ones mined from legitimate sources.)