I was always taught that when you saw one of those people in the street, you were to cough pointedly and cross to the other side.

Get them away from our children!

I’d vote for one for president, but only if he promised to stop it. I don’t think they should be allowed in public places. Sure, freedom of choice, and all that jazz, but really, this is a bit much. What if they get it on me?

When I learned that Oscar Wilde was one, I solemnly burned all his books.

They’re smokers, of course. Sometimes I see them in restaurants and pass them pamphlets with a disapproving stare. It is my duty. They are corrupting the youth.

“I can remember when the air was clean and sex was dirty,” George Burns once quipped.

A mere 40 years ago, you could smoke anywhere and marry your same-sex partner nowhere at all.

Now the tide is turning. Last week, New York state legalized gay marriage. And smoking? In May, Mayor Bloomberg banned it outdoors in New York City’s parks, beaches and public plazas.

These days, if you want to smoke in New York City, you can only do it in a 6-inch-square enclosure somewhere underground. It is dank and malarial and can only be found by people who already know where it is, or if you pay $8 in unmarked bills to a man in Times Square who asks to be addressed as Pumpkin the Rat.

And nationwide, the noose is tightening. The FDA has just emerged with new labels for cigarette packages that are harrowing to behold, with depictions of smoke-damaged children and smoking through tracheotomy holes.

Could it be any more official?

Gay marriage is the new smoking. You can do it anywhere in New York City you would like, and people won’t cough and indignantly cross the road.

And this is emblematic of a larger trend. We don’t care what you do in the bedroom so long as you don’t do it in the street and frighten the horses, as Mrs. Patrick Campbell once quipped — or on Twitter, where the photographic evidence can be saved and used to frighten horses later. We understand that you have little choice in the matter.

Sex is decreasingly immoral. There are entire magazines devoted to it, and to the proposition that “whatever you are doing, trying adding ice cubes.”

Smoking — that’s another story. Cigar enthusiasts get slurs like “cancer-monger” and “death eater” yelled at them as they walk through the street. Smoking, somehow, is too vile to be advertised on television or depicted in films. Since the MPAA adjusted its ratings system in 2007, smoking is more wrong, more perverse and more likely to garner an R-rating than murdering someone very sexily while you curse at him. I recently rewatched for the sixth time a movie set in the ’60s. And nobody smoked. Nobody!

Public morality has taken a turn. We are living in the bizarro ’60s, where you can get married to your same-sex partner while wearing mod-inspired suits but cannot celebrate with cigars.

I am not saying that smoking does not kill people. It does.

I understand that all this harassment of smokers is for our own good. Smoking is wrong and bad and et cetera, and if you steadily blow smoke at your child, it will damage him or her or “Storm.” But so many things are wrong. Driving, for instance. Talking on a cell phone while driving. Eating food. Drinking. Bear-hunting. Hunting bears while drunk. Climbing mountains. Rappelling. Being Grover Cleveland.

But it’s amazing how much vitriol we level against those who indulge in smoking.

Maybe we are delighted to be able to judge someone, for once. In general, we are tolerant of everything all the time. It’s something of a national hobby.

But that doesn’t diminish our fundamental, burning desire to leap to judgment. And we can no longer judge people for who they are. We can only judge them for what they do. Are you overweight? That’s okay. Eat unhealthily? Shame!

The category of Things We All Agree To Be Wrong is so small these days. Smoking has always been a vice. Before, it was a social vice. Now it’s limited to barely 20 percent of the population. They are a hard-bitten crew, sneaking around furtively and paying exorbitant taxes “It will kill you!” we shout. “You pervert! You need help!”

“Ah, but is not all of life a long and lovely suicide?” the smokers say wistfully.

“No!” we shout, delighted to be right. Health is the new standard. You are supposed to jog and abstain and inhale thick lungfuls of pure oxygen. Say what you will about people’s sexual habits, some of them might have health benefits. But smoking? Forget it.

By and large, it’s a good shift. Tolerance! Enlightenment! Onward! But sometimes we need to let our judgment leak out. And increasingly, it’s against those smokers. From here, one can almost glimpse a future where society encourages you to do anything you want in the bedroom or at the courthouse.

Except have a cigarette afterward.