Inflation is sometimes called the hidden tax, but they're not the same thing. The state might also suffer from inflation, it's usually not benefiting from it. Taxes, on the other hand, go directly to the state authorities and are, in theory, used for something that important for all citizens.
Governments and policy-makers are on top of their nations, they belong to elite class and are less affected by inflation while the lower classes in same countries have to struggle more with inflation and their life quality decreases a lot with higher inflation. It's right that inflation affects all areas, all aspects of life and it's only matter of time for people realizing it.
As for how Bitcoin is taxed and whether inflation is cheaper or not, that depends on a specific country, with its inflation rate and taxes.
It's not only about inflation but also depended on stance of governments on Bitcoin and its potential to compete against their fiat currencies as well as how Bitcoin attracts capital among citizens out of traditional markets. If governments see signals of big capital move out of banks and traditional markets, they will try to enforce many extreme hatred of policies against Bitcoin, not only taxation policy.
If you live in a country where it's not illegal to use Bitcoin as a currency, you will not pay capital gains tax when you bought something using Bitcoin, but you do need to pay personal income tax.
If in a country with Illegal status for Bitcoin, and I am living there, I will try to be as most careful as possible with any activity with my Bitcoin and Bitcoin transactions. Big problems can appear any time and I am not ready to face with legal issues carry out by government against me.