HEARKEN to me you steadfast, curly permed, lumpy pullovered women defenders of Tung Tau Estate. I have been into the bowels of the sort of place you have resisted having, not so much in your own backyard as in the Housing Department's and therefore my, the taxpayer's, ground floor. I have been into a hostel for the severely mentally handicapped. Fear not, it was miles away from you, in Kwai Chung, in the centre of Lai Yiu Estate where the resident pedestrians were showing no signs of anxiety. I spent two hours there, unmolested, and if what I saw is what you, the champions of Tung Tau's highly presumed mental cleanliness, live in dread of in your neighbourhood, then you and your menfolk are a bunch of old women. Lai Yiu Adult Training Centre is run by the Society of Homes for the Handicapped in the shopping block podium of the estate. It has a roomy floor with wide corridors because the over-ambitious planners intended it as a shopping level. It had no takers, so they gave it away to a social experiment. ''I want you to make a note that I am now bringing out my key,'' said Mr Stephen Chan, the society's executive director, outside the hostel entrance. ''If opponents of residential hostels think we let our trainees go wandering off, they are mistaken. If they did, they couldn't find their way back and we would be in a terrible fix.'' The key turned to open a quarter of the door, where we squeezed through. Ignorance took a grip. I'd once visited a secure ward of a mental hospital. ''Oh God!'' I thought. ''Loonies. I'll be pawed by Napoleons and schizos in carpet slippers and have to pretend to be relaxed.'' Shame on me. For a moment, I had become Tung Tau man - or woman. There is a distinction between the mentally handicapped and the mentally ill, much wider than that between the sane and the mad. The severely mentally handicapped are the antithesis of the elaborately disturbed or chronically withdrawn caricatures of the psychiatric hospitals. The mentally ill who undergo psychiatric treatment can recover as long as they keep on taking the medicine. If they do, they can emerge hesitantly from a doorway into a Government commercial, get slapped on the back by their sane chums and play basketball. They can function as technically normal people can. The mentally handicapped are different. They are born with an inability to fully develop, to fully adapt to the world of Tung Tau man - or to his levels of aggression or depravity. The mentally ill need treatment. The mentally handicapped need training in almost everything, which is why Mr Chan and his colleagues call them ''trainees''. Through the door, passing trainees stopped and stared, or made a gleeful sort of noise which was appropriate to the welcoming of a visitor. They were so small, almost all of them. It is rare that severe mental handicap does not come with a companion physical condition, too. At Lai Yiu, which has 70 resident and 50 day trainees, speech defects are universal. There are, as examples, 37 epileptics, 13 with Down's syndrome and 10 with cerebral palsy. It seemed so unfair. But there is no point in being miserable or pious. The trainees were cheerful, except for the more reflective one, knees under chin on a chair for whom existence was a preoccupying puzzle. As Mr Chan showed me round, individuals would stand off, giving words of encouragement from places of safety. Others would come forward like one youngish woman who wanted a poster because she liked nice paper. An unusually tall trainee in an unusually stylish hooped T-shirt tapped his forehead against Mr Chan's in a long understood form of greeting. In Lai Yiu, everybody wears his own thing. Hair styles are short and to the point. You have to concentrate to tell the boys from the girls, except that they aren't boys and girls. The minimum age is 16 and the oldest trainee is 55. The unworldly joiningof mental simplicity and physical reduction made telling ages difficult. There are four dormitories, split between the sexes, in rooms that were once meant to be shops. The beds are made of plywood in a fashion unintentionally ''cute''. There are three activity rooms, stocked with a generous pot-pourri of gifts from benefactors - cassette players, table soccer, stuffed toys and a physiotherapy machine which is little used. There is one physiotherapist to every 100 mentally handicapped patients - if that. There is one worker to every 10 handicapped. The world standard is one to five. Private generosity continues. Lai Yiu has an equipped dental surgery from the Rotary Club, manned by volunteer dentists. ''It is better than the trainees having to go outside for dental treatment,'' Mr Chan said. ''It doesn't matter so much then if theybite the mouth mirror off its stem.'' In each activity room is a training timetable. The subjects are basic but crucial - sewing, cleaning the floor, making tea. Going to the toilet features prominently. ''They need to be taught everything. It is a round the clock process,'' Mr Chan said. ''They are like babies in one sense. There is not much in there in the first place. You have to put it in. You have to train to a level of normalisation. You have to encourage self-advocacy, making their own decisions.'' In the social hall, a post-luncheon siesta was supposed to be going on, but decisions to the contrary were being taken. Noisy TV was being soaked up. A young man with firm intentions was jogging round the room. Two others were wearing football head gear - out of fashion I was told, not protection. One woman in a sociable mood took my hand. Her friend took Mr Chan's. We had our pictures taken, despite the woman in the green sweater who thought the shot could be taken through her. One Down's syndrome trainee and another in a wheelchair could not have been happier and, at the time, neither could I. Mr Chan took the hands of two trainees, one a 27-year-old man who is a dwarf, and walked them out of the hostel and up to the shopping podium to show me the wall mural they had created. I watched the slow contented resignation with which the three of them walked and I knew Mr Chan was a candidate for canonisation. He is a realistic saint. ''No male staff member is allowed to escort a female trainee out alone. It is a safety rule. Outings require a heavy ratio of workers and volunteers to trainees. We have trips in small groups and our very active parents groups help but, even so, the opportunities are very much dependent on more volunteers coming out with us.'' The touching trio stood among snacking schoolchildren on the podium. One schoolgirl's lunch box spoon stopped halfway to her mouth as she spotted us, but then I was there so it might have been the gweilo that made her falter. Who, in the clutter of ignorances, could tell? Was it these physically constrained little souls with IQs under 70 who so worried the Tung Tau protesters? Could they truly feel physical threat from pacific, slow-witted people who had to be taught everything from how to cross a road to, in some cases, how to go to sleep? The worst of it is that the Tung Tau protesters knew more about this than I did. The voluntary agencies laid on two buses and took them on an explanatory tour of a similar hostel. On February 21, an exhibition was staged on that estate. Mr Chan believes the mentally handicapped do not really concern those particular tenants. They came lately from the demolition of Kowloon Walled City and are disappointed with their compensation. The hostel protest is a way of getting back at the authorities. Wickedness afoot, indeed, but Mr Chan still thinks they should be eventually converted into volunteers. The same result was achieved with original protesters against a hostel in Shek Wai Kok estate, Tsuen Wan. People like Mr Chan prefer to point out the unexpected best in people. The late Father Tapella and Father Bonzi, founders of the society, first started working in the 1970s with the mentally handicapped in a Kowloon housing estate where they enjoyed appreciation and much support. It was Tung Tau.