One ongoing discussion I have had with a friend is whether pets should be allowed inside or not. My view is that they should (at least for pets like cats and dogs; horses probably should not be house pets). I have this view on non-rational grounds: I grew up that way and it seems normal to me. in fact, it never occured to me to justify my view, at least until it was challenged.
The main reasons given as to why pets should be outside are that they are animals and that they dity things up (fur, literal dirt, barf , slobber and so on).
My reply about them being animals is that humans are also animals and this does not seem to entail that we should not be inside. Of course, some folks see humans as being distinct from animals. While I do agree that (most) humans are people, this distinction does not seem to warrant humans being allowed inside while entailing that all non-human animals should be outside.
The point about animals making things dirty is a reasonable point. After all, I have spent a great deal of time cleaning up after my pets and repairing the damage they have done. It would be easier and cleaner to keep them outside. However, my view on this is that the dirt and destruction are part of the cost/price of having a pet. As with most things, deciding whether it is worth it or not involves weighing the cost versus the value. In the case of my pets, I like having them around me and I feel better that I can see them. If they were always outside, I would be worried that I might not see that one of them was sick, hurt or in danger in time. Also, being outside all the time inceases the chances that they would become sick or injured. For me, the extra effort of cleaning up pet stuff and dealing with the fur problem is a reasonable trade for having my pets. I think the same way about my friends. Friendship comes with a cost, but I find my friends worth the effort.
I do recognize that this is my own subjective assessment. For some people, the mess of a pet outweighs any benefits that having a pet inside (or a pet at all) would provide. In such cases, it would be rational for that person to not have an indoor pet (or any pets at all). Or they might be willing to tolerate pets, provided that someone else did the cleaning and was aware of their concerns about pet messes.
While I am not a relativist about most things, I think that this is a case in which what is “right” is relative to each person. It is a matter of what the person values, what bothers him/her, and how they regard pets. I’m willing to deal with the extra cleaning, the occasional hair in my food, and even dog slobber on my clothes. But, this is my choice and others might have a different, but equally correct, view.