But that's just gross neglect. As a cat owner, I have to deal with the occasional pee on the floor and there are specialized detergents that are very effective in getting rid of the smell.

You do get desensitized to the smell, though. The first time cleaning the litter box I almost vomited, these days it's a mild inconvenience at most. When I get guests, I'll clean the litter box as a precaution, someone else's nose might think the smell is horrible but I'd barely notice it (I don't ever let it get that bad).

I do get the point from a landlord's point of view, though. Why take the risk if there are other tenants who don't carry that.

Although I think it should be negotiable with a larger deposit rather than flat out refusal. Pets increase the quality of life.