It's an unfortuante truth that many pet owners out there are irresponsible enough to allow their cats to go astray and reproduce constantly. As nice as cats are as pets, they can also be a danger, being carriers of disease when left untreated on the streets.
I see euthanizing them as a good means of reducing the problem of stray cats. If there were enough homes to go around for them all then that would be a wonderful thing, but sadly that is not the case. Many people out there would rather buy a cute and cuddly kitten from the pet store than some old, grungy looking stray. The cats, I believe, would be better off in death than starving on the streets of cities, a danger to us as well as other animals.
The idea of hunting them is somewhat amusing to me, but at the same time I can see why some would be disgusted by it. We tend to think of cats as cuddly pets, not vicious animals.
For the record, I've adopted two cats that were once in the animal shelter. When I can afford it I adopt as many unwanted pets as I can. My mother has an even bigger heart for strays, as she has about 7 cats, many many birds and a dog.