Completely agree, Ryan; it's hugely offensive. Are they suggesting that they have some algorithm that has identified us as potential racists and homophobes? If so, a quick glance at my FB friends list alone ought to be enough to disabuse them of that idea.
Personally I think the discrimination issue is just a smokescreen Airbnb are using to achieve their aim of making instant book mandatory for all. My belief is that they have taken a random sample of new hosts as an 'experiment' to see if sufficient numbers will accept it. Some - like me - have not, but the fact that the company are refusing to reverse the policy suggests sufficient numbers have accepted to make it a viable proposition. I'm sure that the next stage of the plan is to make it mandatory for all new hosts and then mandatory for everyone.
Yes, Airbnb know that some hosts will unlist their properties but they also know that established hosts will find it harder to walk away than new ones who are not remotely reliant on the company for income. They will have 'done the maths' and worked out that, even if they lose a percentage of their hosts, they will still make more money in the long term by being able to compete with the likes of Booking.com on the same terms.
I am very surprised that more established hosts have not picked up on this issue as I'm sure it's going to affect them soon. Personally I spent the best part of two weeks getting very stressed about it before I realised I was trying to fight a losing battle with a company that has an entirely profit driven agenda.