I've killed innocent people for free. Spiders, flies, etc. Animals are people too.
Other than your bug here and there, I couldn't ever kill anything. This includes a bird my cat dragged into the house and it was suffering with broken wings, all cut up, still alive, etc. I didn't throw it out while it was alive because it probably would have been eaten alive by ants or something which is worse. After it was dead, I swept it up and threw it into the woods. It would have been more compassionate to kill the bird, but I'm the type of person that "wouldn't hurt a fly," despite the fact that I've killed flies so something else that I wouldn't hurt mostly anything.