Bitcoin is not designed for taxes to be paid on it. I beleive the best for government maybe to tax bitcoin users and make it more popular. Just that the charges should be considerate and proportional to the excesses.
I agree that bitcoin is not designed to pay tax but can it make bitcoin really populer because of tax? Paying tax makes decentralized system owned by bitcoin lose, it won't be your own again because the government interfere on your 'room', so that bitcoin will not be fully under your control again, it's with government's interference.