This is the point where your reasoning goes wrong.

The government isn't threatened by bitcoin. Why would it be?  Right now it is just a nerdy internet cryptocurrency accepted by almost nobody (with the exception of sellers of black/grey market goods and services and hardcore proponents).  It's main userbase scams each other on an alarming scale, and the network  (mining) consists of a neverending arms race that ensures that eventually only the top x% can run it.

Lets be honest, this whole thing will collapse itself eventually....it doesnt need the governments help.