Early on — actually, it was before I even moved here — I learned a key lesson about exploring downtown Atlanta’s south side: Don’t bother.

My wife and I took MARTA downtown, exited at Five Points and headed south on Broad Street beside the former Rich’s department store. A group of loitering louts started in with loud and lewd descriptions of her. I registered annoyance but was greeted by caustic stares that told me to shut up.

A couple blocks of drab urban scenery later, we turned around and went elsewhere.

A quarter century has passed since then, but I thought of that first impression last week when I heard that a south downtown condo dweller got punched after calling 911 on a new generation of ne’er-do-wells.

Robyn Jackson lives in a condo in the Kessler’s building at Broad and MLK Jr. Drive. He was walking his dog when he thought he spotted drug activity and called 911.

Calling police has become routine for Jackson and his partner, Stuart Jackson. Broad Street just south of their loft resembles a Dystopian society of loud, animated people hanging out until all hours, drinking, selling drugs, urinating, fighting, sometimes even shooting, and urinating some more.

After calling the cops, Robyn Jackson waited outside. A man ran up, accused him — correctly — of calling 911 and then punched him twice in the chest. He said he waited almost another half hour for police to finally respond.

Jackson and Jackson, who coincidentally have the same name, have been fighting the same battle for years. Two years ago, Stuart Jackson told troublemakers that doing drugs out in the open was illegal and he was calling the cops. A man screamed at him and shoved him. It seems the Jacksons just don’t learn.

Stuart forwarded me a dozen of the many emails he has sent to seek help from the police and Central Atlanta Progress, the downtown business coalition. The email subject lines tell the tale of a societal breakdown just a block from the heart of Atlanta.

Here’s a sample: Help us another homicide in Downtown Atlanta. Broad Street Bandits Gang in Downtown. Another shooting on Broad Street at the barbershop. Assault at 100 Broad. Vagrants and drunks at 91 Broad. And, my favorite, Trashcans on Broad Street being stolen in broad daylight.

A Central Progress director responded to him: “It appears 10 have been stolen. Fortunately, they were the old ones. I cannot explain why they weren’t bolted, but we are fixing that.”

It wasn’t supposed to be like that. Stuart Jackson, a CPA, moved to the loft in 2000 in the old Kessler’s department store, which dried up in the 1990s after Rich’s closed across the street. It was an old brick building with tall ceilings, near the Georgia Dome and a block from MARTA’s main station.

“This was supposed to be the start of such a great change here,” he said. “This was in the middle of what was happening. Kroger was still open. Mick’s (restaurant) was still open. Underground had the Gap.”

As we spoke in front of their condo, a young man in a white T-shirt walked by and loudly stated: “Leave the people alone or you’re gonna get hurt.”

I don’t know if it was a threat or some friendly street advice. The tone seemed to carry the former.

Today, Broad Street just south of MARTA is a lifeless block dominated by the fortress-looking rear of the Sam Nunn Federal Center. The block south of that, where mayhem simmers, has several largely vacant old-timey brick buildings that are painted a kaleidoscope of colors to hide the fact it’s a dying block.

A business owner leaving work summed up his survival strategy: “To protect myself, I look the other way. To me, trying to do right brought me trouble.”

The man, who didn’t want his name used, said he once called the cops to report a drug entrepreneur plying his trade outside. Minutes later, the officer dragged the druggie into his business.

“Is this the guy?” the cop inquired.

“I don’t know what you’re talking about,” the businessman responded.

While we spoke, a car drove up to the small crowd outside. The driver sells $1 shots of booze, the businessman said.

Police Major Wayne Whitmire, who heads Zone 5, said south downtown “hasn’t been forgotten,” it just hasn’t received the same attention from the business community or other Atlanta civic powers.

“It’s not against the law to hang out,” Whitmire said. He said the slow response on Jackson’s call to 911 may have been because it happened at a shift change.

“The complaint is that we’re not out there,” he said. “Well, we’re out there; we’re out there a lot.”

The major said that two of his zone’s 12 beats converge on that block and “we’ve locked up 1,389 people so far this year” in the two beats. That includes 269 drug arrests and 593 quality-of-life crimes.

The aggravating thing to Whitmire — and this complaint is so frequent that it’s deja vu — is that criminals are arrested dozens and dozens of times. For the “toxic element,” Broad Street is like their workplace. They are just showing up to their jobs.

“We see people out there with 150 arrests,” he said, his voice growing incredulous. “Why are those people out there in the neighborhood?”

Whitmire argues there has been change for the better — a contention the Kessler’s residents dispute.

“It’s not a fast process, but it’s coming,” the major said. “Perception is a lot harder to fight than reality.”

This week, the developer who plans to re-build Underground Atlanta told the Business Chronicle that the retail/residential/techie biz tower that he envisions for the site could include up to $400 million in new investment. The city, which is helping build a new Falcons stadium blocks away, is sure to get behind an effort to clean up that area. Right?

Well, back in 1990 when I was writing off south downtown as a destination, the newly renovated, $142 million Underground was not yet a year old. You remember that place. You went there once, didn’t you?