If I pay bitcoin tax, where is the anonymity? It means the government knows where I live, my wallet address, probably the exchange I use and the amount I used in the exchange. If the government should know that much then they can control the use whenever.
I don't think it means any of that. All you have to do is report that you bought them, then spent them, and if you took a loss or made a gain. Just like you do with fiat. Hell, going along with the system and reporting all of your bitcoin transactions might even be a good thing. It could show the government that this thing is for real. And since it's digital by nature, keeping records will be easy, there are already a lot of services out there that help you with it.