I'm not a cat lover, but history has taught us that removing a predator, like a wild cat, to save a prey animal, in this case birds, usually results in an uncontrolled abundance of prey animals.
By naturally controlling the population of birds the cats are making sure the birds don't over populate the area and become pests.
History has also taught us that the introduction of a non-native predatory organism into an ecosystem can result in decimation of vulnerable native species.
Tabby, Ginger, and Cuddles are no more a "normal" part of the North American ecosystem as purple loosestrife and zebra mussels.
And mice.
By naturally controlling the population of birds the cats are making sure the birds don't over populate the area and become pests.
Of course, but any number of hunters want all of the game to themselves. A feral cat taking one pheasant in one year is one less pheasant for a hunter to shoot.
My late father was a hunter and a cat lover. One day, he brought home a number of dead pheasants and showed one to the original Siamese Princess, a now elderly seal-point Siamese cat. She let out out a loud yowl of alarm! I guess she was more accustomed to lusting after the small sparrows and starlings that she saw from the window. The pheasant was too big.
I agree completely, but in this case the cats are prey and we are controlling them. Granted, bullets could be a little extreme, but have you ever tried to catch a cat that didn't want to be caught? It's funny that we love certain animals, love to eat some animals, and love to exterminate some too.
I once went to a restaurant in China where they had all kinds of "cute" cat pictures on the wall. Best meal I ever had.