So let them require BnB's to be registered and inspected. If I start a single-room restaurant, where people can join me at the dinner table each night (and yes, those exist: a few have been popping up in some European countries lately), it wouldn't be outlawed either, would it? I'm sure hardly any owner would mind paying $100 a year and allow random inspections (which usually means they'd get inspected once every two years or so...).