This isn't about your arguments not making sense, it's about someone who wasn't listening to them, because if he had listened he would have risked being convinced. You shouldn't have to defend your no, certainly not in that kind of situation, but a similar discussion with someone who was actually prepared to listen to anything other than "great, please give us an application" would have been shaped differently.

If the difficulty had been about your arguments making sense, he might have either offered to have the place cleaned, or said that "smells right" was "ridiculous," but not both.

I suspect that if you had given a more commonly understood kind of reason, like wanting more light or disliking the shape of the kitchen, that realtor would still have pooh-poohed it and claimed that you would have to settle for that.