Hmmmm, good question, @Allison2. TOUGH question. One of the reasons I use Instant Booking is because I recognize the importance of counteracting my own prejudices and trying to treat all potential guests equally. And I agree with @Allison2 and others who say that shutting out people just because they have views I don't like probably feeds prejudice rather than fighting it.
So, I want to think I that I would be willing to host these folks, even if I wasn't totally comfortable with it. But then I am white, Christian, cisgender, and have never been the target of a hate crime. I can't help thinking about how I would feel as a person of colour or a Jew and facing the prospect of having my home filled with strangers who likely promote, and possible commit, such crimes. That would take a courage I can't even imagine. And, even if some hosts were willing to do this, I am not sure it would be OK to EXPECT it of them.
AirBnB has a responsibility to treat its clients fairly, for sure - regardless of their religion, beliefs, race, gender, etc. But I believe it also has a responsibility to protect its hosts. The question, of course, is how to balance those two things.
I think AirBnB made a reasonable call on this one, but I would be really interested in hearing the perspectives of hosts who belong to minority groups.