My (admittedly anecdotal) experience with taxing an addictive/harmful thing "for people's own good" is that it just results in said people cutting their budget to afford the tax, making their life worse overall. This ranges from heroin addicts somehow always finding the daily $$$ to fund their dose, to people mildly grumbling about the price of cigarettes yet buying them anyway.
On the other hand, forbidding a thing altogether seems to have disastrously ineffective results too (see: the prohibition, war on drugs, etc.).
Maybe a better solution is to simply forbid companies from putting addictive things in their products to sell them, but keep the addictive thing legal, e.g. don't put too much sugar in the soda you make (so people won't expect too much sugar as a matter of course) but let people add sugar to the soda if they really want to. In other words, regulate companies' practices but not individuals'.
On the other hand, forbidding a thing altogether seems to have disastrously ineffective results too (see: the prohibition, war on drugs, etc.).
Maybe a better solution is to simply forbid companies from putting addictive things in their products to sell them, but keep the addictive thing legal, e.g. don't put too much sugar in the soda you make (so people won't expect too much sugar as a matter of course) but let people add sugar to the soda if they really want to. In other words, regulate companies' practices but not individuals'.