However, there are ways to earn bitcoin if one has the skills and the patience. And this can be just enough. Sooner or later bitcoin will be unbanned and one can find himself quite a HODLer at that point. Of course, it needs trust and patience at super high levels.
I agree that you should not be buying/selling bitcoin if it becomes illegal in your country. However, you can just do that elsewhere, where it is legal.
One can travel abroad and spend their bitcoins there, where it is legal. Or he can just sell it in an international exchange and move the money to an bank account in another country.
In the end, the only people who will suffer with BTC prohibitions are the ones who doesn't have much money or don't have the information to trade in another location. People with money and/or information will always find a legal way to buy/sell bitcoin (unless we are talking about a global prohibition of btc, which is quite unlikely to happen)