Robert K. McNamara, a Howard County planner, spent the past year writing a 251-page document that has managed to irritate nearly everyone from home owners to home builders in this county wedged between Baltimore and the District.

McNamara, 32, regards his comprehensive rezoning plan--Howard's first since the late 1977 and the subject of an emotional two-hour hearing earlier this week--as a blueprint for judicious growth in a county whose population of 130,000 is expected to nearly double over the next 20 years.

But longtime Howards residents, developers and farmers already are calling for major changes--or the outright defeat--of the recently released proposal. "Everybody's got an ax to grind," said McNamara, a genial, boyish-looking official in Howard's Office of Planning and Zoning. "The planning board, zoning board, citizens, developers--a lot of folks are dissatisfied."

McNamara and other planners expected some outcry over the rezoning plan, but reaction to the proposal has been unusually harsh, they said. Earlier this week, at the first of three scheduled hearings on the proposal, several residents lambasted the plan as a "sell-out" to developers and a threat to their neighborhoods and life styles.

Many objected to proposed changes in regulations that would allow "floating zones" of low-density housing; a new zoning category for medium-density housing that gives developers the option of building eight housing units per acre; and a new category of "planned employment centers."

Howard's leading developers, meanwhile, contend that the rezoning amounts to a "no-growth" plan, a proposal that sets aside a mere 2,500 acres to new industry and allows for the construction of only 7,000 new housing units over the next two decades.

"The bottom line on this plan is no growth," said W. Patrick McCuan, the chairman of the board of The KSM Group, a Columbia-based developer of residential, industrial and commercial building. KSM, with $40 million in projects annually, is a leading competitor with the The Rouse Co., Columbia's other large development firm.

"Howard County is so strategically located, its potential so high . . . that it's a failure to allow only 7,000 new units over the next 20 years," said McCuan. "Why, in the '70s, 2,000 units were being built every year in Howard."

McCuan charged that one planned zoning designation--a category called DR-2, allowing two detached housing units per acre--would make construction of affordable housing in the county virtually impossible. "The county doesn't understand that in today's market, duplexes, town houses and other attached units may be the only housing that people can afford," he said. "Our hands would be tied."

McNamara, however, said the DR-2 category--and the similar DR-3 category with its eight-unit option--would give developers more flexibility in designing subdivisions. Both designations would relax lot-size requirements, allowing housing to be built around common open space instead of along conventional subdivision patterns.

Such concentrated housing "would save developers on road construction and utility costs," McNamara said. "A developer could shave the cost of a house, pass the savings on to home buyers."

Some community groups, meanwhile, argue that the new residential designations--DR-2, DR-8 and a category for garden apartments--will open the door to high-density housing in or near neighborhoods of half-acre or acre-sized lots. "The whole face of the county is facing major changes," said Judy Rivkin, an Ellicott City resident and president of the Howard County Community Association, a coalition of 10 civic groups.

Rivkin and other community leaders also said another new category allowing "floating zones" of attached housing on sites of at least 25 acres deviates too widely from the general plan Howard adopted last year.

"Floating zones give developers complete discretion on where to locate such housing," said Bob Solem, a Defense Department employe long active in local zoning controversies. "There aren't any tight controls over a zone like that--except that the site be a minimum of 25 acres."

Planning officials thus far have recommended no land as future "floating zones," McNamara noted. "The general plan says, 'Thou shalt not change zoning in stable areas,' " he said. "If the floating zone is ever approved, it would be in the nature of a special exception.

"A developer would have to prove that his project was compatible with the surrounding neighborhood."

If opponents in the three-sided debate over Howard's future land use agree on nothing else, they all regard theirs as a county at a crossroads.

"I have sympathy with people who live here," said McNamara, who worked as a planner in York County, Va., "and can understand their wish to see as little change as possible. But it's irrational to expect no growth in an area like Howard."