The real risk is to hold onto a specific moral ideal - not because having moral ideals is wrong, but just that sometimes they cannot be (reasonably) held onto (philosophically). It may broadly make sense and be a perfectly fine rule-of-thumb, but eventually it becomes a square peg in a round hole.
Taxes can be theft, but until someone's lifestyle is perfectly free of negative externalities and is perfectly free of inherited blood-wealth, one's wealth is never truly completely theirs - there are legitimate moral claims upon it that will never erode. This means that there are actually types of taxes that are not theft. Cutlass is correct, it doesn't matter if the spending by government is 2% or 50%, it entirely matters what is being spent upon.
After that, it's all just haggling; the haggling is fine and even necessary, but it doesn't come from a position that can be argued as a moral absolute. I absolutely believe in objective morality, but "taxes are theft" isn't one of them.
