That is making the assumption that government spending is constant irrespective of tax revenue. If tax rates and public debt remain constant then tax avoidance will lead government spending to fall. This may mean fewer immoral actions conducted by the government such as wars or arresting people for victimless crimes. In this way, tax evasion can be not only harmless but a moral imperative.

Do you not see where this is going? You could make exactly the same argument in favor of stealing government property.