if bitcoin was seriously threatening the dollar as the nation's medium of exchange and interfering with monetary policy it would be extremely easy to shut down its mass use as a medium of exchange
Perhaps, but you would have to define what constitutes a serious threat. Personally, I think the serious threat to dollar and global monetary system is emanating from monetary policy of the global monetary system itself. The Fed, ECB, BoE, BoJ are all engaged in co-ordinated efforts to drive up asset prices in the attempt to induce some form of an inflationary effect.
It's not working very well so far. This is the biggest threat, not bitcoin.
Bitcoin is simply emerging as an asset class benefiting from this monetary policy. There is no real indication that it will be used broadly as a medium of exchange anytime soon and in the narrow pockets where it is being touted, say on PayPal, I don't think there is any intention on their part to use bitcoin to evade their responsibilities under the financial regulatory system? In other words, they will declare their holdings and transactions in Bitcoin and will be subject to the appropriate tax regulation etc.
My own view is that, because of the internet and the digital age that we live in, bitcoin is asset class for anyone and everyone. It offers an opportunity for everyone with an internet connection to obtain a degree of economic and financial autonomy that the prevailing banking system has failed to achieve in 300yrs.
As I'm prone to say on occasion, "
If the men of property will not support us, they must fall. Our strength shall come from that great and respectable class, the men of no property."
In the context of bitcoin, the prevailing order of money printing for the "too big to fail" classes versus austerity for the rest is coming to an end.