Fast food should be taxed just enough to pay for the problems it causes, as should everything else. We shouldn't be encouraging or discouraging anyone from behaviors we believe to be morally repugnant. Instead, we should only be de-externalizing costs that parties to a transaction bear upon others.

We should structure our society for maximal freedom -- that is, such that one can do whatever one wants so long as it does not restrict the freedom of another. A de-externalizing cost-recovery tax does exactly that. Anyone who disagrees with me prefers to make others pay for their poor choices and thus hates freedom, not to mention personal accountability.

C'mon, people. Stop hating freedom. Like, seriously.