You can only be forced to do so if there is a record of the transaction taking place. You may be legally obligated to pay taxes after selling some gold to your buddy, but that doesn't necessarily mean the law is enforceable in that situation.
So you basically say people are not forced to use fiat, because they can violate their "legal obligations" ?
I'm just drawing a distinction between being forced to do something and being potentially threatened with force. You could say that in 1933 all US citizens were "forced" to give up their gold, but in reality they did not all do so and the coins are still around to prove it. If you are a law abiding citizen and categorically refuse to pay capital gains taxes, you do have the option not to perform trades that would result in you owing such taxes.
You can also sell firearms off-the-record to a 'buddy' or a shady character, even if a license or transfer fee is required by the ATF.
You might grow pot at home, sell it to some friends and not tell anyone about it because it's 'harmless'.
You are still taking a risk of imprisonment every time no matter how small you perceive the risk to be.
No argument there. Life is full of risk though.