This attitude is what I see as Bitcoin's primary risk factory. It's a culture of arrogance that reminds me of pre-crisis finance, when it was popular to say things like "the Federal Reserve chairman is more powerful than the U.S President."
It's very easy to ban - make it illegal to sell Bitcoin, force ISPs to block international sites that do.
The Bitcoin code is open source. Anyone from anywhere can download the code and run a local copy. Your coins are securely stored across computers all over the world. Your balance cannot be frozen by any authority. Maybe central exchanges that convert fiat to Bitcoin could be regulated, but mining cannot be stopped, transactions cannot be stopped. Unless governments all over the world shut down electricity and internet.
At that point question mark is on the government that does this rather than Bitcoin.
Please lets not start this debate. Times and times again it has been proven that software is not secure. OpenSSL was also thought to be secure for quite some time too..
That does not mean it's secure, but at this point it's looking more secure every day.
Bitcoin itself cannot be stopped, but it's utility as a currency (or, as it is now, a speculative investment) can be.
Whereas with the internet, if someone is able to knock out critical infrastructure one day, engineers would figure out a way to fix/reroute it, get it working a few days later, and everyone would happily log back on as soon as it's working. Although maybe they would throw out their "smart" coffee machines and etc.
There have been crashes of bitcoin before. None "to zero" but pretty substantial, and not everyone "cashes out" right away.
But the previous crashes weren't caused by any real news of a significant weakness of Bitcoin, so if there was news like that, then the crash would be worse than we've seen.