How long have they had the rabbit? How old is it? Perhaps printing off some pages about "house rabbits" would help copnvince them it can be an inside bunny. Lots of people do not know rabbits are able to be housebroken, maybe they don't know. If they take it inside and play with it every day, obviously they care. Do they have other pets it might need to be protected from inside? Never assume ignorance is intentional - gie them information and a chance! After all FloppsyLadySally's bunny got to come inside!