That's partially true. Off the top of my head you can convert it to bullion fairly easily [1][2] and there are DNM cash out services on most DNMs too, a lot of trust there but if you spread it out over multiple vendors and smaller transactions you could convert it to physical cash. Each transaction increases your risk of detection by postal police and by just getting ripped off by the seller or the mail carrier though.
[1] for example JM Bullion (and others) accept bitcoin https://www.jmbullion.com/buying-gold-silver-bitcoin-faq/
[2] some sellers on /r/pmsforsale will accept bitcoin occasionally.
I suspect that banning cash would result in an ad hoc barter system for goods and services. If people are engaging in economic activity they want to hide from the government, and find others willing to engage in the same activity, they'll probably work something out, right? Whether it's masks that could potentially hide someone from facial-recognition cameras or something else.
A casual interaction between shopkeeper and customer would never be facilitated by barter in such a hostile environment.
It's the sort of thing you spend a few years normalizing instead of implementing in one fell swoop. Rapid changes unnerve people and a rapid elimination of cash could cause civil or economic unrest. I believe India has experimented with demonetizing larger bills, and in Sweden businesses that accept cash are becoming increasingly uncommon, as are people who use cash.
When the majority no longer consider cash important, eliminating cash becomes safer. More people adopt the mentality that cash users are criminals with something to hide or generally just paranoid weirdos, and are consequently less likely to object when the use of cash is further restricted. Moreover, with fewer people using cash, the government has largely achieved their objective already. When few people use cash the haystack the needles are hidden in becomes much smaller.
Regular people who don't care about privacy or censorship resistance will use credit cards. This is in the interest of the powerful because you can easily disable service for undesirables.
The rest will use Bitcoin
Further, if something's illegal in a different jurisdiction than you are in, you aren't usually exposed to any liability, as any tourist to Amsterdam will tell you. And not having a payment record doesn't change the fact you did it and will undoubtably have left other evidence.
Once again, these are social problems that magic beans won't solve.
You may not be exposed to liability back in the US, but that doesn't mean your Visa/Mastercard will necessarily work if you're doing something illegal in the US: https://www.cbc.ca/news/canada/toronto/square-canada-1.53031...
These are again, very much, social and not technological problems that require cryptocurrency.
In Canada for instance, you can easily get a merchant account with Moneris (a Canadian payment processor) and take card transactions over Interac (the Canadian debit network). Yeah, Square's bound by their US banks, because they're a US company with an overwhelmingly US product being sold internationally.
Ironically the government here in Ontario will sell you marijuana by mail and they accept Visa and Mastercard! The rules must be very vague and inconsistent.
My mental model was like yours, and like friends in college who fantasized about road trips to another state or Canada to find a bar that would serve 19 year olds. Not all laws are about the location of the act. Countries can and occasionally do bar their citizens from doing things anywhere, as was the case of Cuban goods.
There's also some weird extradition stuff that's been floating around lately that I can't make heads or tails of. There's definitely some fearmongering going on around it but I don't know if that means I should be concerned or dismissive.
And then there's one little idea. This may be crazy, but if the citizens of your country generally agreed that something was dirtbag behavior, you going somewhere where there is no law against it still makes you a dirtbag. Just a law-fearing dirtbag.
Ex post facto requires maintenance and vigilance, like any piece of safety equipment. Don't just count on it always being there. We all have to work at it.
So because the root cause is a (probably unsolvable) societal problem, we should just forget about technical workarounds like Bitcoin?
This whole thread reminds me of the early South Park episode where all the Catholic diocese...s? meet to figure out how to stop getting caught molesting children.
You could stop molesting children. That would definitely work.
This is the HN discussion when that article was posted a year ago:
https://news.ycombinator.com/item?id=16687008
This is the r/Monero discussion where people much smarter than myself talked about the article's shortcomings:
https://old.reddit.com/r/Monero/comments/87hr28/hn_discussio...
It's hard/impossible to prove a negative.