What I believe here is, Fiat is under the control of the government and they have the ultimate power to control their citizens. Secondly, fiat is being issued under government control whereas bitcoin is a decentralized digital currency, which cannot be controlled by any government.
Thirdly there is limited trackability of bitcoin as compared to fiat.
Yes, it's true that most governments are against bitcoin but what I believe here is that strong legislation should be done in order to the utilization of bitcoin under the government's regulations.