Possibly happen if the government joined to Bitcoin, also if they seems that Bitcoin will earn a lot, they can use them power to manipulate the Bitcoin live in the market. Because if the price in the market were high, government will gained them.
If the government comes in to the situation, the price of bitcoin will even increase. The more coins that they buy, the more the price will increase. It becomes harder and harder for them to buy more bitcoins.
That's the only way for the government to manipulate the bitcoin price other than spreading FUD about bitcoins. They have to accumulate bitcoins first before they can manipulate the price
I don't think this is the only way
In fact, there are quite a few ways in which a government could affect Bitcoin prices (provided they ever wanted that in the first place). I don't think that the PBoC ordering Chinese exchanges to disable both Bitcoin withdrawals and deposits can be (mis)interpreted as FUD. It is a direct intervention using administrative leverage, any way you look at it. As an extreme measure, they could just outright ban Bitcoin or confiscate coins pretty much in the same way they did with Silk Road. And that will crash prices provided this government is influential enough (like that of the US or China)
But who knows? Maybe the government has a huge part in the bitcoins of circulation. Maybe they bought the majority of bitcoins right from the start when it's still cheap so they can take down bitcoins at the right time.
You could just as well claim that Satoshi himself is actually a government agency