Doesn't this meen that if china bans crypto, then all privacy coins will explode in price due to higher demand from chinese users?
Well, probably not. The majority of crypto wealth comes from banks, hedge funds and other financial institutions. You and I are merely pawns in this whole process. If it becomes illegal then none of these groups could afford to conduct illegal activities.
You also have to remember that encryption and bypassing the great firewall is also illegal. No large organisation can wilfully break the law.