As with all other forms of prohibition, the banning of bitcoin would merely stimulate a black market for the digital currency. At this point the genie is out of the bottle, and there's no turning back. Bitcoin is a legitimate currency, as Japan has recognized. Some nations will ban it, which will only hurt them in the long run.
Yep, Bitcoin won't go away if it gets banned. It is nearly impossible to monitor. The government doesn't have the resources to keep up and track every Bitcoin transaction, so it would still be used. With that said though, it would definitely hurt Bitcoin a lot, because many people follow exactly what the government tells them in terms of propaganda... and if they made Bitcoin out to be something shady that was illegal or only used to buy illegal things then it would not be good. Like you said, any government that does this will end up regretting it in the end.
I want to ask a question why it would be banned. What will happen? Is bitcoin illegal? If not so then I do not understand why bitcoin will be banned?
). But, yeah, I think, many people who are using bitcoin will make a rally against those who will ban bitcoin. There's no enough reason for any departments or big agencies to ban bitcoin. And I also believe that bitcoin will never be banned in general. 
