Discussing the problems with a soda tax is both easy and difficult. It is easy because the main argument is fairly obvious: If taxing soda in the name of public health is a legitimate function of government, then there is no functional limit on what government can do under the guise of public health.
But this argument, though straightforward, is a difficult sell because it is not terribly convincing. This is partially because it is a slippery slope argument (“step 1 will inexorably lead to step 10”), and slippery slope arguments are often straw-man arguments. Arguing against step 10 (“so why don’t we just tax all bad foods?”) is not actually the argument being made at step 1 (“I think we should tax soda.”).
The other reason the argument is difficult is because it is hard to ignore the science. Perhaps it is true that a tax on soda will help public health. In fact, I’ll concede for the sake of argument that taxes on soda will increase public health.
So, as someone who opposes soda taxes, what arguments do I have left if I’ve made these concessions? There are three: 1) The Primitivism of Politics; 2) The Modern Fallacy of “Public Health”; and 3) A Properly Formulated Slippery Slope Argument