Supporters of this kind of paternalism consistently claim that slippery slope arguments are irrelevant and there's no nefarious grand agenda underlying this new rule. Adam Ozimek at the blog Modeled Behavior has a challenge for these "non-paternalists":
I think it would be useful to for critics of the slippery slope theory of paternalism to demarcate now what future policies would constitute evidence that they are wrong, because my guess is the point of demarcation will move right along down the slope with policy. Several years ago many of todays critics of slippery slope theory would have said that an attempt to regulate salt would constitute evidence. But now, farther down the slope, salt regulation is just sensible policy.
So, what paternalistic policies would make these so-called non-ideological pragmatists squeamish? And will they still be squeamish in ten years?
Unfortunately, here's the answer: nothing is off limits for the food paternalists. The pattern will hold. In ten years, a new study will come out proclaiming that something we always thought to be safe (let's say aspartame) turns out to have negative effects late in life if consumed in excess. More studies will come out. The elite bureaucrats will issue warnings. Local jurisdictions will restrict it, and then ban it, in the name of common sense regulation. The non-ideological pragmatists will praise this courage. The bans will scale up, and all the while, supporters will sneer at the idea of a slippery slope, because it's merely the science that says they are correct.
Here's the real problem: many, many things can have negative effects if taken in excess. Paternalists therefore want to abolish individual responsibility and replace it with government-mandated moderation. For paternalists, there are no limits to what junk science will tell them is so bad that it must be regulated, restricted and banned.
Hat tip: Bryan Caplan
Update: Caplan suggests that anti-paternalists put up or shut up as well. So here's mine: soda containing high-fructose corn syrup will be banned in a local jurisdiction within the next decade.