Even if the world did, how could the stop it?
Bitcoin is just currency. No government can stop two people from using something as currency for exchang of good and services.
For example, if i fix your roof and you pay me as compensation, how can any government interefere with that personal transaction?
Let's get some examples of how a government could ban Bitcoin. China hasn't even banned Bitcoin, they just won't let you buy Bitcoin in China with yuan.
Not quite. Bitcoin is PROPERTY, and unless you ban private property there is no way to ban Bitcoin, unless you believe in communism which does ban private property. Governments control fiat federal money and as such they can attempt to ban or regulate transfers between their respective national currencies in their exchanges, but unless we turn to communism (and communists still do exist and promote such socialistic concepts)there is no way to ban Bitcoin.