This is correct. However a huge part of the any currency's value is the number of people who believe in it having value (as a means of payment and\or repository of value). While a ban doesn't affect the ability to exchange Bitcoin , it will reduce the number of people willing to exchange their fiat money for it, thus driving its value down.

Gold survived to this day as an asset because it has never threatend to replace the dollar, the yuan or the euro. If Bitcoin stays within the assets domain, there is a bright future for it. If it pushes to be fully recognised as a currency, it is destined to be fought by governments around the world.