I think you should all try to find out if the shelters in your area put down ferals automatically and if they do, spend a little time educating them about ferals.
In the old days, when I first started bringing home young cats off the street and accustoming them to eating at my house, there were a lot of dramatic incidents -- still are sometimes -- where trapping the cats was the only way to get them to the vet for shots and neutering. But I quickly learned four things --
that older cats who have always been ferel generally cannot be touched, but will gradually use your house as a stopover in bad weather or when they are hungry (this means you can keep them current with their vaccinations and also trap them and take them to the vet when they are sick or wounded.
that older cats who, after a few weeks, come to eat when called and gradually work their way into the house have probably been house cats at some time or other but because of abandonment or mishap they lost their human families.
that kittens that do not know a human touch before 6 to 8 weeks are in what I call a "soft-feral" state -- which means that, if they hang around long enough getting good food an conversation (progressing to light touches on the head while they eat, and slowly to petting them , and progressing slowly), they will eventually move in with the household...and it is well-worth the effort, since some of my sweetest and most home-loving cats came from soft-ferals.
And finally, that kittens rescued when they are younger than 6-8 weeks old accept humans and any cats or dogs within the household very quickly -- some within minutes, but most within a few days.
I do not look for very young cats, but children (and some adults) bring them to me. Generally they are born in the wild and something has happened to their mothers. The children know I will take the babies in and bottle feed them, and every year there are one to 10 or 11 such kittens delivered to my gate. Last spring there were one litter of home-nurtured kittens that the owner was desperate to get off his hands (they were leaving Israel for a job abroad) -- 6 weeks old -- and 3 feral kittens that he had been throwing food out for near his place of business -- around 8 to 9 weeks old). The home-grown kititens took about 2 or 3 days to stop hissing at me, and the ferals stopped at about 2 weeks (but I could touch them and pick them up anyway almost from the first day -- a few minor scratches, but we are all used to that...).
These kittens are all happily part of the family of 21 cats and 6 permanent house dogs. Last week (it is the second of 3 kitten seasons in Israel per year), I was brought 2 little ones who were near death -- six or seven weeks old, but with the physical maturity of 2 week-olds (we could tell by the well-developed teeth and very strong claws). In two days they were happily being adopted by several of the dogs who rather love little kittens, and were smart enough to identify me as the food-giver to come when I call them.
The vet hospital where I take them were initially astonished at the progress made by cats, whose initial visits had to be examination through the mesh of a crush-cage or under anesthesia, and whose second or third visits we made with no gloves and no scratches. Now they take it for granted, and some of the vets and staff have begun to take in ferals with good success.
Education and demonstration are the key to changing people to recognize that a savage cat is usually -- like a savage dog -- a demonstration of terror. They have to learn to trust.
If you want to do a good deed, you will try to form groups of cat owners who have or are willing to adopt ferals. You might then be able to persuade shelters to take a more modern view of things. I changed my vets from hating to deal with ferals to learning how to handle them successfully in ways other than violence or anesthesia. After two visits when I first started, they began to ask me politely if the cat could be touched and then taking my word for it. But mark -- I NEVER let them handle my cats unless it is one that is totally socialized to visitors in my home. I ALWAYS hold my cats myself for whatever procedure is called for. If anyone is going to be scratched it is me. And that doesn't happen to often (I'm getting more clever at HOW to hold them so they can't leap up or twist or get their hind claws in contact with soft human anatomy).
Anyway, spend a little time re-educating the shelter people, and next time demand to be allowed to adopt ferals. Once spayed or neutered, they can, if they like, roam freely but come to you for food and comfort -- not bothering anyone and being healthy enough to be loose.