When 74 percent of San Francisco voters last year backed legalizing the adult recreational use of marijuana statewide, the idea was to make it easier to buy and smoke pot — a substance that has never been that hard to buy or smoke in San Francisco anyway.

Tell that to the San Francisco Board of Supervisors.

The Keystone Cops of Cannabis have spent countless hours over endless committee meetings in recent weeks, devising ways to dramatically limit where people can buy and sell marijuana once the substance becomes legal for recreational use statewide on Jan. 1.

Sure, nobody wants San Francisco to turn into one big year-round 4/20 celebration, and figuring out how to regulate a new industry takes time. But City Hall is taking its weed worries to bizarre heights.

No cannabis shops within 1,000 feet of schools! Or day care centers! (Because you never know when a toddler will waddle out of his day care center unsupervised and trade his peanut butter sandwich for a blunt.)

Only one dispensary per commercial corridor! No cannabis shops at all in Chinatown! Or West Portal! No more than three in the outer Excelsior! Or within 600 feet of each other! Or to the north of a sushi restaurant or the south of a yoga studio or below an overpriced condo — no way! OK, I made those last ones up.

Progressive San Francisco circa 2017 making a hash over regulating soon-to-be-legal pot? You’re not high. It’s reality, prompting one legislative aide to wonder whether she was actually working for the Orange County Board of Supervisors.

And what’s even stranger is that these very same city leaders — some of whom seem to be buying into the reefer madness of the 1930s — are holding these discussions within yards of people openly injecting themselves with heroin and other drugs and strewing their dirty needles around Civic Center Plaza, the Tenderloin and Mid-Market.

Has the highly disturbing, open-air injection drug use that has proliferated in recent years around City Hall — including near playgrounds, schools and day care centers — prompted the same long, fretful discussions and myriad proposals to limit it? Nope.

Politicians are literally walking past people shooting heroin in broad daylight on their way to meetings about drastically limiting the sale of legal pot.

“I wish weed was our problem!” exclaimed Tomiquia Moss, executive director of Hamilton Families, which runs a shelter for homeless families in the Tenderloin. “If that was all people were doing, it would be a whole different ballgame.”

She recalled working at the Tenderloin Neighborhood Development Corp. 10 years ago and marching with families to City Hall to demand that their kids not have to walk around injection drug users on a regular basis.

But the problem only grew worse. Moss said that drug deals and injection drug use regularly happen in front of Hamilton’s family shelter, with little kids inside.

The Tenderloin has the highest number of kids per capita of any neighborhood in San Francisco, but I’ve never heard anybody propose keeping injection drug use at least 1,000 feet way from their schools and child care centers.

“If this was happening in other neighborhoods, it wouldn’t be tolerated,” Moss said.

Diane Van Stralen, program coordinator at the Bay Area Women’s and Children’s Center in the Tenderloin, said she’s seen a lot more people shooting up in the neighborhood in recent months.

“It’s terrible for these kids to walk down the street and see people injecting,” she said. “It used to never be quite as blatant.”

But if supervisors are tying themselves in such knots over regulating legal cannabis shops, how will they ever open a safe injection site for intravenous drug users, as recommended by their own task force? Unlike cannabis, after all, such a site is not legal under state law. And it hasn’t been approved by city voters.

I personally think it should be opened, to help get the blatant drug use off the streets and keep the dirty needles away from kids and other passersby. The supervisors say they’re committed to opening one, and Supervisors London Breed and Malia Cohen told me they’re open to centers in their districts.

“Are you kidding me? I’m a leader,” Cohen said when I asked her if she’d back one in District 10. “My walk has been backed up by my talk.”

Let’s hope the talk about that goes a whole lot smoother than the pot prattle.

Now, there are two entirely separate pieces of legislation regulating the cannabis industry, which the full board may or may not vote on Tuesday. Supervisors mostly say they like a citywide, uniform cannabis plan — unless other supervisors get special deals for their districts, and then they want them too.

“I’m starting to understand Mitch McConnell’s pain in putting together votes in the Senate,” Supervisor Aaron Peskin quipped the other day.

One of the two proposals is close to the original legislation offered by Mayor Ed Lee and Supervisor Jeff Sheehy. The other has all of the proposed amendments dumped into it.

Some key differences? The first version would go with the state’s rule of creating a 600-foot buffer between cannabis shops and schools and would keep pot shops 300 feet away from each other. Those seem like entirely sensible proposals.

The second version would expand the buffer to 1,000 feet and add day care centers, nearly eliminating the “green zone” where cannabis shops could open. The second version also has the specific neighborhood plans like the Chinatown ban.

Lee now backs the 1,000-foot buffer between pot shops and schools, spokeswoman Deirdre Hussey said, adding that the mayor “feels it is critical that the board engages on this complex issue.”

Supervisors Jane Kim, Katy Tang and Norman Yee are the biggest backers of the plan with the 1,000-foot radius and day care center restrictions. Kim has argued that her district already has so many medical cannabis dispensaries that her constituents have plenty of access to pot already. Tang and Yee took great pains to tell me that it’s not because of their own personal views about pot, but because they’ve heard so many concerns from their constituents.

“If you’re smoking walking down the sidewalk, the chemicals can go in the open doors of the child care centers,” Yee explained. “This is what I’m hearing from people.”

Yee said he’d be willing to limit the radius to 600 feet if day care centers are included. He’d also be willing to have one cannabis shop in West Portal, if other neighborhoods take the shops, too. Several supervisors sound willing to compromise, though it’s unclear whether they can get the regulations in place by Jan. 1.

Asked whether she thinks the supervisors should be working to limit the injection drug use right outside City Hall, Tang said, “Absolutely! I totally think so. We just happen to be working on cannabis right now.”

OK, let’s get that done and then move on to injection drug use, supervisors. Tenderloin families have been asking you for help for long enough.

San Francisco Chronicle columnist Heather Knight appears Sundays and Tuesdays. Email: hknight@sfchronicle.com Twitter: @hknightsf