Banning bitcoin is pretty easy even in democratic country, because Bitcoin users are just a tiny minority and a lot of people haven't even heard about it. Take for example weed - 52% of Americans over 18 have tried it at least once, yet the government wages war on it. And although it's impossible to kill Bitcoin, they can certainly hurt it - if they will go after miners, which is very easy to do with their giant power consumption, we will lose the hashpower that secures current value of transactions in blocks, and they can even turn that hashpower against us if they will use seized mines to attack the network. ISP's might try to block or slow down all Bitcoin-related traffic, so we will have to use Tor, which will have negative impact on block propagation speed. Buying at selling Bitcoin would also be pretty hard if it will be outlawed, meaning less liquidity. To sum it up, lets just hope that it won't be outlawed by any major government.
I second your concerns about what could be done regarding bitcoin in most democratic countries, although I think if a government behaved likt that it would anything but democratic. It seems to me Venezuela could do that in the near future, given the massive demand for bitcoin in the country and the plans to launch a state coin soon.
But overall, I think we're seeing a movement towards legitimization of the network (which could always have its downsides).