- You're underestimating their capability to shut down trade in bitcoin. Sure, they won't be able to stop you from running the software. But they have the ability to stop any transfer into/out of the digital world. That part is quite easy to proof: real-world usage of bitcoin requires exchange for regular currency. And bitcoin was founded on the belief that governments have too much control over the flow of currencies. (This argument hints at a common mistake in the tech community: overestimating the power of technology and underestimating the power of law).
- You're overestimating the governments' wickedness. Functioning democracies work on a default-legal basis, and it appears to me as if a to of governments have found a good balance b/w ensuring existing mechanisms are applied to bitcoin, without creating unnecessary burdens blocking its adoption.
You overestimate the willingness of the police force to prove that they are willing to risk their lives and die for what they believe in. In fact, they won't. Ultimately, they count on the army to do that, who won't either.
Sure, but if the US gov makes bitcoin illegal that means most of the buyers and sellers - regular people - have to withdraw from the market.
Many of bitcoins biggest owners are big name dudes - like the twin brothers from Facebook, the Winklevoss own something like 10% of all bitcoins.
If they perceive a change in law, they'll have to sell their bitcoin before that happens, as will all legit owners ... it will flood the market and might very well crash it.
People keep saying that, and they keep being wrong. Think of all the illegal things that happen over bitcoin. There are lots of people who would want to shut it down if they could.