Like I said, I wouldn't normally kill animals. I don't go around killing them for revenge or anything like that. If all it took was a swipe, a yell, to get the cat off my back, that's all I'd do. But you never know what an attack will be like until you experience it. I once saw an 'animals attack' show which had a scene where the cat literally chomps on a guy's crotch. Now of course that's gonna hurt like hell. If a cat does that to any part of my body, I'm gonna pull it off me and do whatever it takes so it doesn't take ANOTHER chunk out of me. If it keeps coming at me, I'll do what it takes to make it stop. If it means the cat's death, well, so be it.
It's all well and good to love animals and not want to kill them, but you'd be amazed what searing physical pain can do to your sense of self control.