Because China Gov owns around 200,000 btc and this is a lot. More than US government. By reasoning, their voice is bigger compared to US government in cryptocurrency.
Should we take china words seriously? No. Because they been trying to ban since year 2013. Then they un-ban and then they ban again. History repeats.
No idea where you got such a figure from and it is blatant misinformation unless you can prove otherwise. If China were to ban it, chances are they would have dumped all their coin far in advance - not that you could trace ownership back to them anyway. You should be careful about spreading such lies because it makes you look very foolish and untrustworthy. Either way, Bitcoin has more than recovered from the initial slump since this news came out weeks ago and is even heading back past all time highs. I think in the long term it will actually be a good thing for Bitcoin because it proves that even the Chinese government is able to take control and abuse this currency.