I think the key to eliminating most of this behavior is to not show the picture right off the bat since it allows people to be subtly racist. If they have to as

I think the key to eliminating most of this behavior is to not show the picture right off the bat since it allows people to be subtly racist. If they have to ask for a picture before denying a guest then it's a lot more obvious they're being racist. The more overt racists can be dealt with by doing simple analysis of denied/cancelled bookings and banning them. I'm guessing AirBnB will eventually have to implement one or both of these approaches to avoid discrimination lawsuits.