Feral cats are common carriers and spreaders of toxoplasmosis, feline leukemia, various worms and other diseases. They carry and transfer parasites such as fleas, ticks, lice, mange mites etc. I don't shoot them, but if the next guy wants to, good on him!
I have a neighbor that will pay to have trapped feral cats spayed and neutered plus full veterinary checkups and care. If that's her thing, good on her.
One way or another, something needs to be done when it comes to feral cats.