NEW YORK -- For fashionable women cloaked in luxuriant furs, a leisurely stroll along Fifth Avenue has become fraught with danger. One recent Sunday afternoon, a cordon of protesters loudly berated and booed patrons outside Fred the Furrier. "You're wearing a dead animal. That's pretty disgusting!" an activist with a bullhorn shouted at a woman wearing a silver fox coat. Chanting "Down with Fred; fur is dead," protesters thrust blown-up photographs of trapped animals at unsuspecting fur-clad pedestrians. Many of their targets simply scurried away. One woman made obscene gestures at the hecklers. "I'm more careful about where I wear my coat," said Thomasina Fiorella, an East Side resident in a full-length mink, adding that she had heard stories about fur wearers being sprayed with paint. New York City, widely considered the capital of the $2 billion fur industry, has become the target of an unrelenting crusade against fur by a national animal-rights organization called Trans-Species Unlimited. About one-third of U.S. fur sales are made in the metropolitan area. Daily harassment of fur wearers here reaches a peak on Sundays, when hundreds of pickets frequently turn out at Manhattan's swankiest fur boutiques. "Business is bad," said Glenn Rutherig, a wholesaler on Seventh Avenue. "People are dumping their inventory. Sales are off, I think, partly because of the economy and partly because it was a very warm winter. But these anti-fur people definitely had an effect." Twice, he said, activists used Krazy Glue on the metal door locks of his store so he could not open. Lois Doherty-Mander, a Manhattan executive who sports a full-length mink, said that, "if these animal rights people are going to strive for a nonviolent, pacific way to better the world, it doesn't behoove them to use scare tactics. If they took a more Gandhi-esque attitude, they might have a more sympathetic audience." Steve Siegel, executive director of the New York chapter of Trans-Species, said fur wearers are "selfish people who don't care about the 50 minks that were killed for one mink coat." By embarrassing them publicly, Siegel said, "we're giving selfish people a selfish reason to stop wearing fur coats, even if they don't give a damn about the animal." But Tom Riley, a spokesman for the Fur Retailers Information Council, called animal-rights activists "a vocal minority who shouldn't be allowed to thrust their opinions on others and stop the freedom of choice." He said the council monitors the animal-rights movement. Riley said that the movement has become "a very profitable business" but that many of its followers "are being deceived and misdirected." He said he was "appalled" at hearing that some donations were being used to defend activists accused of violent acts against fur retailers. An estimated 10 million Americans contribute to dozens of animal-rights groups, whose goals range from protection of endangered species to such esoteric causes as elimination of woolen clothing because sheep may be nicked in the shearing process. One group recently waged a campaign against bacon and eggs, which it dubbed the "breakfast of cruelty," while another liberated six lobsters from a Chinese restaurant in Rockville, Md., and let them loose in the waters off Maine. Siegel, 39, a mild-mannered former schoolteacher who works out of a small office in lower Manhattan, seems an unlikely revolutionary. Trans-Species, he said, is a "missionary organization" dedicated to eliminating violence against animals "whether it's at the rodeo, the fur farm or the laboratory." He said the group opposes several activities, including pet breeding, cattle wrestling, leather manufacturing, hunting and fishing. "Fish are just animals that live in the water," Siegel said. "Their mouths, where the hooks go in, are very sensitive. People who say fish have no feelings are just kidding themselves." The portrait of the activist has changed, he said, "from an older female who is cat- and dog-oriented to young, educated, politically motivated people." Many are so-called "vegans" -- strict vegetarians who refuse to wear animal products or use cosmetics and other goods tested on animals, he said. While most groups use peaceful means to convey their message, some extremists have raided research facilities to free laboratory animals and set fire to fur outlets. Riley said the fur industry documented at least 350 incidents of vandalism last year, more than double those during 1987. A fur store in Santa Clara, Calif., was torched, he said, storefronts have been splashed with red paint, and windows have been the target of BB guns. An underground network called the Animal Liberation Front, which is on the FBI's list of domestic terrorist organizations, has claimed responsibility for many of the acts. One case here involves Fran Stephanie Trutt of Queens, who was arrested last November for planting a bomb at the headquarters of U.S. Surgical Corp. in Norwalk, Conn. The company uses dogs to train medical personnel on application of surgical staples. Investigation revealed that the company had hired detectives to befriend and spy on Trutt, leading Trutt's lawyer to argue that she was a victim of entrapment. Marianne Scipione, a company spokeswoman, said that "we think we acted prudently" because Trutt had "made death threats" against company Chairman Leon C. Hirsch. Dana Stuchell, a cofounder of Trans-Species Unlimited, said that, while her group does not endorse illegal activities, "we understand the motivation behind it. With any movement you're going to have people on the fringe who take the law into their own hands and follow their consciences." Siegel said Trans-Species makes its point without violence. Last year, after a Trans-Species letter-writing campaign, a Cornell University medical researcher halted a federally funded, drug-addiction study that involved cats. The group plans soon to sponsor "Meat Out," a day of protest against meat eating. Members are to picket a midtown McDonald's restaurant with signs reading "McDeath." Last November, Trans-Species and 100 grass-roots groups staged the third annual Fur Free Friday in 68 cities. Here, 2,500 protesters marched down Fifth Avenue in the largest known anti-fur demonstration. They were led by Bob Barker, who quit after 21 years as emcee of the televised Miss USA pageant because the officials insisted on giving away a fur coat on the show. The activists think they have cut into the industry's profits. Siegel said the three major retailers -- The Fur Vault (Fred the Furrier), Antonovich, and Evans Inc. -- reported losses for the 1987-88 season. And designers Bill Blass and Carolina Herrera announced that they would discontinue their fur lines.