When I say that any one or any gov can take out Bitcoin at any time I"m talking about a 51% takeover of the mining community. It would cost right now around 20 million. but This DEC it could cost as little as 8 million.
True, if you'd like to hamper the trust of people into Bitcoin and are willing to spend the few millions there's nothing stopping you. Mind however, that often such obvious and drastic attacks can backfire. For example: after such an expensive attack, people nowadays downplaying the relevance of Bitcoin might rethink their position.
EDIT: once you gain 51% of the network you could if you wanted to be an ass hole raise the transaction fees a lot
Nope, that's not possible, even if you had 90% of the hashing power, low-fee transactions would still be mined by the remaining (friendly) 10% and clear within a few hours - which sounds reasonable for pretty much a worst-case attack scenario.
or if you wanted to be really evil you could do a double spending attack. With so much fraud no one would trust the network and it would go belly up in a matter of days.
It would be a major turmoil in Bitcoinland for sure and many would lose trust, but proof-of-stake forks of the blockchain with any double spends etc. reverted would probably pop up and gain traction in a matter of days. Besides: no hashing power of the world can spend coins that were in your possession before the attack started, so the long term saving quality of Bitcoin would remain unaffected.
Even with such a major attack Bitcoin would not just go belly up - in the end it would probably come out stronger than before: technically more resilient to such attacks and implicitly legitimized by the adversary who feared it so much that it was worth planning and executing a large scale attack.
If you really want to harm Bitcoin, then do it the more subtle and slower way of lobbying for laws and regulations making it harder to do legal business with Bitcoin.