The basic case against New York Mayor Michael Bloomberg’s latest crusade, to outlaw the sale of extra- large sugared soft drinks, is Libertarianism 101: In a free country, people should have the right to do what they want, even if it’s bad for them.

The major exceptions and complications to this basic principle don’t seem to apply. Unlike secondhand smoke, my consumption of a Pepsi does no direct harm to anyone else. Unlike marijuana, sugary drinks have a perfectly adequate and legal substitute: sugar-free drinks. (Even if you can tell the difference between Coke and Diet Coke, you can’t claim that the difference is very large.) And unlike a regulated pharmaceutical drug, a single dose of Coca-Cola won’t kill you.

Furthermore, there are less intrusive alternatives to an outright ban: You could require more prominent labeling of all soft drinks with their calorie counts and let people decide for themselves. Or you could apply the rule only to children.

The basic case in favor of Bloomberg’s proposal is in some ways even more compelling: Bloomberg is the founder and majority owner of Bloomberg News’s parent, Bloomberg LP, and therefore my boss. In all likelihood, therefore, he is right about soft drinks and sugar, just as he is right about almost everything. (And even that “almost” is only there as a sop to my dignity.)

As if that weren’t enough — which, of course, it is — there are other important factors arguing in favor of Bloomberg. We have a serious obesity epidemic, especially among children, and desperate times call for desperate measures, not for philosophical niceties.

Another consideration: The law, as currently proposed, would be comically easy to evade. It wouldn’t apply to sugary drinks bought in supermarkets, rather than restaurants and entertainment venues; or to sugary drinks made with (at least 51 percent!) milk, such as a Starbucks Frappuccino or a milkshake; or to large amounts of soda purchased in separate containers.

A law with so many easy ways to get around it almost surely won’t be effective. I’m not sure whether this goes into the “good” column or the “bad” one. You can argue it both ways.

With so many loopholes, a law like this is no real threat to our liberty to guzzle flavored sugar water. Nevertheless, it sends a powerful message of social disapproval. So that’s good. On the other hand, it’s not a very persuasive argument to defend a restriction of liberty on the grounds that it won’t really work. So that’s bad.

Soda Scofflaws

One final consideration: It’s not quite true that your bad habit of guzzling sugary soft drinks has no effect on me. Under the national health-care reform law, insurance companies must accept all comers. They cannot discriminate against you simply because you have terrible dietary habits and are almost sure to develop complications such as diabetes as you guzzle your way through life. Thanks to worthless bums like you, my insurance rates will be higher. So this is one in favor of the mayor.

A few months ago I went to dinner at a steakhouse in New York specializing in huge hunks of aged beef that violate every precept of healthy eating. Let’s not even discuss the fries or the desserts. Because the restaurant is part of a chain, it is required, under one of Bloomberg’s other mandates, to indicate the calorie count for each dish on the menu.

It was a revelation. A hamburger turns out to have 1,800 calories! I’ve been off beef pretty much ever since.

So nannying does work. It has worked as well in the case of banning cigarette smoking in public spaces. I was initially opposed to this, on libertarian grounds. The secondhand smoke argument seemed far-fetched in an outdoor open space like a public plaza, and the intention seemed clearly just to stigmatize smoking in general, in order to get people to quit (or not to start) for their own sake.

But the results have been so dramatic that my libertarian instincts have been overwhelmed. During the 1990s, about 70 percent of high school students said they had tried smoking a cigarette. By 2009 the percentage was down to less than half. Regular users peaked at 36 percent in 1997 and were below 20 percent by 2009. Frequent users went from 12 percent in 1991 to 7 percent in 2009. Thousands of lives have been saved.

In the end, whether you support Bloomberg’s crusade or oppose it depends on how you weigh the various factors. Libertarian absolutists will have no problem rejecting all the above considerations, most of which are pretty trivial, and concluding that freedom is freedom. At the other extreme, health policy types (many of them authoritarian in habits of thought) will have no problem saying that sugary drinks are bad for you and therefore you shouldn’t be allowed to guzzle them in excess, especially if you are a child or young person.

Finally, there are those primarily concerned with keeping their jobs. These people feel that even if Mike Bloomberg happens to be wrong in this particular case, he is so overwhelmingly right about everything else that he deserves a pass on this one.

Michael Kinsley

Michael Kinsley is a Bloomberg View columnist.