Is this a hypothetical question or are you being forced out of your home?

If it's just hypothetical, I'd move, and get a letter of recommendation from the landlord. He already knows I have cats and has no problem with it (although last he knew I only had 5) and knows we take good care of the house and the cats.

If it's a real situation then I'd check your lease to see if it forbid owning cats in the first place. If it doesn't say either way or does allow cats, then I'd pursue that with him with a landlord tenant lawyer. If it does then you are out of luck.