Then governments will go ahead and break Bitcoin if they so choose.
Or, more likely, they will require all merchants and banks and exchanges and everyone else to reliably prove that the Bitcoins they have just accepted were not from an illegal source or were part of a money laundering transaction. Just like they are doing with cash today. Which you can't because that would "break bitcoin". Which will mean, that you won't be able to use Bitcoin to buy anything in any developed country. Which makes it a fun experiment but after all pretty much useless.
There will have to be some kind of assurance that basic standards of AML assurance are maintained. Otherwise Bitcoin can never break out of it's current role and go "mainstream". Governments will simply not allow it and while they can not shut it down, they can make it effectively worthless.
I absolutely agree that blacklisting is pointless and stupid. I also think we will have to think of something else to achieve the desired effect.
Cash is accepted everywhere without proof to show it hasn't been laundered or obtained via illicit means, so I'm gonna go ahead and call bullshit on that. Also, governments aren't going to waste "their" money enforcing rules on something they're not going to profit from. There's no incentive for them to want to regulate it.
The US has already said they have no place in regulating it, so you might wanna go buy mintchip or something if you think regulation is the way forward.