If bitcoin was banned then it will be a huge issue because a lot of people are doing their best in bitcoin and they are all collecting bitcoin and keeping it on a safe place for an expected return which can make them a rich person in the future. Bitcoin is a really great currency but even a simple banning decision from a country for example in China, then it will affect the whole market again just what happened in ICO banning.
I think there are many attempts from governments of banning bitcoin but its not an easy for them to destroy such a decentralized system because the system is between the user and the blockchain through internet maybe they should have to shutdown first all internet network in order them to succeed but not will never be happen since the world is running by internet, but I think there are government that are now slowly adapting to crypto currency.
It is easy for them to destroy the cryptocurrencies because they have the control under their country and by making a law or order, it will easily ban the cryptocurrency and if all of the countries or governments will do the same then the decentralized system will become useless because everything is under control by the government and that is the truth.