We know it wasn’t irony that died in the terrorist attacks of Sept. 11, 2001 — as if! But there were nonhuman victims, including our sense of balance, proportion and fun. And our common sense.

Thursday’s arrests of participants in the Occupy L.A. movement for writing and drawing its messages in chalk are just the latest examples of crazy overreactions to harmless art projects, with one of the first taking place in Boston, Somerville and, of course, Cambridge.

1. The Mooninites invade, 2007

Guerilla marketing for the “Aqua Teen Hunger Force” movie went awry Jan. 31, 2007, as Boston police and elected officials totally freaked out over the LED boards, thinking they might be bombs. After essentially shutting the city down for hours, the Boston bomb squad even blew some up, though you’d think a bomb squad would be able to tell when something is a bomb and when it is not. For instance, are there explosives? Is there a transmitter? If not: Probably not a bomb.

In this case, these 20 devices were definitely not bombs, just battery-powered boards that looked like a Lite-Brite representation of the movie’s Mooninites giving passers-by the finger. An Arlington marketing guy was arrested; Boston Mayor Tom Menino gave grave speeches about how “it is outrageous, in a post-9/11 world, that a company would use this type of marketing scheme”; Daniel Conley, district attorney of Boston’s Suffolk County, said we should all hold Turner Broadcasting responsible for the horrors it wrought; Attorney General Martha Coakley prosecuted tenaciously and humorlessly, ultimately settling for community service and a public apology from the men who planted the devices; and the media inveighed against the evil marketers for their “hoax devices,” forgetting that for the devices to be hoaxes the marketers would have to be involved in some kind of deception, and — tellingly — wondering why everyone under 40 seemed in on the gag.

Nine other cities were seeded with the Mooninite ads; none reacted like Boston.

New York, though, had its chance to totally lose it some five years later.

2. Reasons to hate, not heart, New York, May

The “hoax device” mentality hadn’t faded five years later. Brooklyn artist and furniture designer Takeshi Miyakawa, 50, was arrested May 19 for hanging illuminated plastic “I ♥ NY” bags in Manhattan and Brooklyn’s Williamsburg area as a contribution to the year’s International Contemporary Furniture Fair. Panicky New Yorkers thought they were bombs, which is fair enough — but police arrested Miyakawa, charged him with reckless endangerment, criminal nuisance and “planting a false bomb” and gave him a 30-day sentence on Rikers Island (he served three) and a mental evaluation.

Again, shouldn’t police know better? Once they look at the bags and see there’s nothing inside but LEDs and batteries — no explosives, no transmitters — shouldn’t that be the end of the matter? At the very least, is it proper to charge someone with “planting a false bomb” when the planter was doing no such thing? A false bomb is one that either is made to look like a bomb or proclaimed one, and no one is saying Miyakawa did any such thing. (Except the police, who are the experts the citizenry relies upon to make judgment calls that show actual judgment.)

If Miyakawa was walking a poodle down the street and panicky New Yorkers called police saying it was a lion, would the police charge him with “walking a false lion”?

In the cases of Boston and New York, where two blocks had been evacuated, police and other officials seemed to be responding based on how they reacted rather than the actual level of threat or the intent of the people they blamed.

Miyakawa is scheduled for a July 19 court date.

3. L.A. police crack down on walk-by chalkings, Thursday

Here’s the thing about chalk: It washes off. This is why parents buy sets of Crayola sidewalk chalk for kids and how the kids have gotten away with using them in countless communities across the country for an equally uncountable number of years. But on Thursday in Los Angeles, police and elected officials decided that when adults pull the same shenanigans with political intent it’s time to kick ass.

The result: Four officers injured making 15 arrests and a whole lot of weirdness.

“They decided they were going to turn ArtWalk into a protest,” LAPD Capt. Horace Frank told the Los Angeles Times, explaining the need for the arrests and showing his extensive knowledge of how art is never used to protest anything. (See, irony isn’t dead.)

Frank also said chalking is not a protected form of speech, calling it mere “vandalism,” and he got support for this bizarre assertion from a bizarre source: Eugene Volokh, a professor of constitutional law at the University of California at Los Angeles, who agreed government has a role regulating writing with chalk on the sidewalk. In fact, “state law governing vandalism was changed in 2000 to include the use of any medium, including chalk,” the Times said.

To top all this off, the Times ran a photo of a worker spray painting over Occupy chalking, showing the city’s extensive knowledge of how chalk can’t be washed off with water.

So here’s the other thing about chalk: If you write things using it, that’s just as covered by the First Amendment as if you do it with a pen on a notepad, in a newspaper column, video, blog, television spot or with a massive political contribution from your corporation. And vandalism is destruction or damage to public property — is the public property in Los Angeles somehow more prone to being damaged by chalk than, well, any object anywhere?

Is it really okay to just redefine vandalism and the First Amendment because people who write things with chalk aren’t typically beloved by police?