Presiding over a rally honoring the Los Angeles Kings for winning hockey's Stanley Cup, Garcetti reminded everyone there are two things an elected official should never do in public: appear with a drink in hand or let loose with a four-letter word.
Then he broke both rules, waving a beer bottle over his head and shouting, "But this is a big f — ing day."
He wasn't the first politician to use the F-word, of course. President Richard Nixon used it all the time, as history's Watergate tapes confirm. He just never said it in public.
Garcetti's decision to cross that line Monday demonstrates that it probably won't be much longer before many other elected officials do the same, said pop culture historian Robert J. Thompson. After all, Thompson added, everyone else already has.
"I can walk across campus any day and hear well-brought-up, polite students sprinkle their language with F-words and S-words, and they aren't even angry. This is just the way they talk," said Thompson, director of the Bleier Center for Television & Popular Culture at Syracuse University.
It was different 20 years ago. When U2's Bono used the F-word during the live telecast of the 1994 Grammy Awards, there was a national outcry and the Federal Communications Commission launched an investigation. But when Bono did it again at last year's Golden Globes? Well, who even remembers that?
Beloved Boston Red Sox star David Ortiz also let the word slip last year during a televised event honoring first-responders to the Boston Marathon bombings. The chairman of the FCC himself responded on Twitter that it was no big deal.
"David Ortiz spoke from the heart at today's Red Sox game. I stand with Big Papi and the people of Boston," said Julius Genachowski.
Such events are an indication, said Thompson, that as powerful as it once was, the F-word is going the same way as such predecessors as hell, damn, crap, snafu and a couple of others that, while they still can't be printed here, are said everywhere.
"Within 30 years, I think it's going to be almost completely neutered," he said.
One reason is that you hear the F-word all the time now on cable TV and the Internet. But another, Thompson said, is that people who use it these days often don't even think of it as a vulgarity describing a sex act. To them, it's just a colorful word.
So much so that when UCLA linguistics professor Pam Munro and her students published their most recent campus slang dictionary in 2009, not a single student suggested flagging it as offensive. Munro said they did want racial slurs flagged, however.
Not that throwing out the word won't still result in some blowback, as Garcetti learned this week.
Although the mayor's spokesman did not respond to calls and emails asking about the public's reaction, scores of people freely expressed it online.
Among the 100 or so postings on Garcetti's Facebook page, opinion was divided. Supporters noted he hadn't said anything different from what most people have said. Critics, however, denounced him as a jerk, a wannabe hipster and a bad influence on children.
Garcetti himself indicated he might agree with the latter criticism.
"Kids out there, do not say what your mayor said today," he offered during a Monday night appearance on "Jimmy Kimmel Live."