Localbitcoins is the best way
Find someone with fiat in the real world, organize a trade in the real world, he gets crypto/you get fiat.
What's there to lose?
If you are really paranoid, I suppose that the IRS might ask the NSA for your phone GPS movements, browsing history, bank transaction records, and might pay a detective to investigate you and prove that you bartered crypto for fiat on the open market and did not include that in your transaction history for tax submission.
Now imagine the government trying to do that on a scale of tens of thousands of individuals.
A) They are as of yet (as far as I know) completely unprepared for that
B) They probably are trying to come up with a way of doing that now, but how long before they can actually start going after people?
If you were smart, you would have made enough profits by then to flee the United States Incorporated and would have moved most of your assets outside of the US to a small, relatively low-key country, where you could develop your property and live a life connected to the world-wide-web where you were always in an extremely beneficial position.
By then, the US would have turned into a corpotocracy (a kind of fascist/technocratic society where the government is just the armed forces of the corporations). If you still lived in the US, most of your rights would have been taken away and thousands of your compatriots would have already been locked up in jail for doing things even less bad than that
So what do you want to do?
We're entering turbulent times... ''Desperate times call for desperate measures'' is as good of a motto to have as "If You Are Not a Liberal at 25, You Have No Heart. If You Are Not a Conservative at 35 You Have No Brain" as mikethenutt nikethemutt put forward above.