1. That's illegal :
2. It will crash :
3. Anyone clear in its head wouldn't use it :
4. Bitcoin at a bigger scale would fail :
1. Government backed and regulated currencies are manipulated even more than bitcoin with unlimited inflation and US government printing dollars without anything backing it other than simple virtual trust on their economic power.
2. Pure manipulation only can't create such constant growth of bitcoin price, the growth we are seeing is just natural which corresponds to increasing demand where as supply is limited.
3. Anyone clear in its head would buy bitcoin and store it for future.
4. Bitcoin at a bigger scale will actually get more success and value that it has right now, more community support means stronger bitcoin network.
Look at the currency in India and a Venezuvela, the governement can easily confiscate people's wealth.