Howard Stern declared himself a "good Samaritan" yesterday - saying he felt a duty to help cops grab the screaming, spitting madman who accosted the shock jock and his girlfriend on a Manhattan street.

Speaking out on the incident, first reported in yesterday's Daily News, Stern told his listeners his girlfriend Beth Ostrosky wanted him to stay with her Saturday night after they escaped the ranting lunatic who hocked a "big loogie" in her face.

But Stern said he decided to go help cops capture the assailant to protect New Yorkers.

"She wanted me to just stay there with her, but I said, 'No, this guy's dangerous,' " the Sirius satellite radio personality said. "You can't let this guy stay on the street."

A rattled Stern called cops, who picked him up and drove him around the upper West Side looking for the attacker.

With New York's Finest backing him up, Stern himself searched the inside of a nearby building where three men were hanging out, but he didn't recognize them.

"We got back in the car and they pulled over a guy on the street," the radio host recalled. "I said, 'Yeah, that's the guy!' and to be sure I called Beth, who came over to take a look at the guy, and it was him."

The homeless ex-con, Gregory Forbes, 50, allegedly charged at Stern about 8 p.m. as the couple strolled home on Columbus Ave. after dinner - getting within inches of the radio gabber's face and screaming, "Howard!"

Forbes got enraged as the couple tried to scurry away near W. 62nd St., and he raised his fists to Ostrosky, yelling in her face, Stern said.

"I told her to go on ahead, run, go home, leave, just go, and I'll deal with this. She said, 'No! Let's just go faster,' but I knew it was something I had to deal with," Stern told his fans.

Following the couple for two blocks, Forbes mumbled some more threats as Ostrosky jumped in a taxi and begged her longhaired beau to follow, Stern said.

"This guy comes over to the cab like he's trying to jump through the window," Stern recalled. "And [then, he spat in her face - into her mouth, her face and her eyes. She's freaking out."

Stern, 52, escorted Ostrosky home to their luxury high-rise before setting out with cops.

"I did what any good Samaritan would do," he said. "After Beth was okay, I felt obligated to find him, because he could do something to someone else."

Forbes, who last lived at a Hamilton Heights boardinghouse, was hit with menacing and harassment charges. He was being held on $500 bail.

Ostrosky was all smiles yesterday before bringing her British bulldog, Bianca Romijn-Stamos, to get prepped for a dog fashion show. Dressed in jeans and sneakers, the leggy blond said getting spit on was "gross."

"This is New York. I want to be able to walk down the street," Ostrosky said. "I still feel safe. It was just an isolated incident."

Forbes long has been a nuisance to New Yorkers, allegedly terrorizing workers at the posh Dylan Hotel in midtown last year and using candy to lure a kid from a Harlem school in 2000, sources said.

Since 1990, he has been busted eight times for offenses ranging from drug possession to sleeping in a park, the sources said.

The very private Stern said he decided to speak publicly about the incident after the front-page exclusive in yesterday's News.

http://www.nydailynews.com/front/story/405738p-343525c.html