(This is not the first time, nor the second time, nor the third time, that we've seen the news "china bans bitcoin" or "china cracks down on bitcoin".)
It only needs to crash once.
And as basically everyone knows but refuses to acknowledge, the liquidity limitations of all this speculation (i.e. there's nowhere near enough demand to buy up a dropping currency) mean that it'll crash all the way to zero when it does.
I'll grant you bitcoin is volatile and "dangerous". That's true before China "bans" bitcoin. But the question is "did China just ban bitcoin" and the answer is "most probably not".
Speculative investments have boom/bust cycles, they always will. Arguing that bitcoin is somehow immune is silly.
And, specific to bitcoin, when that crash happens it's going to be catastrophic. Daily-trade-to-capitalization ratio for bitcoin is literally 10x lower than it is for any other volatile security. When the owners start fleeing there will be no one to buy.