To ban Bitcoin you just have to ban fiat transfers to exchanges, something banks can easily do.

And that would take the banning of any instrument like a gift card. How exactly do you think you could do that?

They don't need to ban all Bitcoin trading to effectively wipe it out as a significant source of money laundering. Gift cards are not what money launderers want because they are hard work to turn back into real cash. What are you expecting people to do - post giant packages of iTunes gift cards to China in order to buy BTC?

I think a lot of bitcoiners are in denial about how reliant the system is on tolerance by the authorities. If you can't move money in any significant quantity to exchanges then ransomware usages will go away (along with other usages). Even if residual trading by hard-core users continues it won't be at a scale that is large enough to care about.