Yes, it is ethical. House cats are by nature acclimated to life among humans. There are, of course feral cats. They usually still seek help from humans. Domestication of animals is a good thing in many instances. of course in dogs, and to a large degree, cats. I see a big difference here in Texas though. People will let dogs and cats out anywhere, like discarded trash. Animals along a line of descendants who have been domesticated for centuries. I believe God meant for some animals to be companions for us.