The manipulators are stealing bitcoins from the miners, who have chosen to sell their bitcoins on an exchange at an agreed-upon rate? Should we ban silver market speculators from trading in fiat too? They're crashing the price of silver all the time! (Of course, the price of silver, like bitcoin, has been in an upward trend in the long run, despite these short-term "crashes".)

You still haven't answered the key question about this type of regulation: who will enforce it?