It is never acceptable to kill an animal to save another animal.
Here's why:
* Animal cruelty is illegal and unethical. Every animal deserves to be treated with respect and compassion.
* There are safer and more humane ways to protect your cat. If a dog is threatening your cat, you can try to separate them, provide your cat with a safe space, or contact animal control.
* Killing one animal to save another creates a cycle of violence. It sets a dangerous precedent and doesn't address the underlying issue.
If you are facing a situation where your cat is being threatened by a dog, please seek help from a qualified animal professional or animal control. They can provide safe and effective solutions to protect both animals.