this is one of those things that is so hard to quantify because it is so hard to have an open discussion in the open. For example, it is easy to have a discussion about more mainstream topics with people who are not into them. People might not be gay, but they can talk about people objectively who are and discuss that they should not be discriminated against etc. You can't really talk about that with zoo related topics, except on here, and most people here are supportive.
I honestly think there is some curiosity out there in the really real world amongst people who would probably never actually do anything, but i still think it is pretty small percentage of people who are actually zoo. there might be a growing number of people who are curious or at least not anti-zoo, but again, it is really hard to quantify that.
I only talk about these topics here...and well, this is a supportive audience so not a good indicator of the rest of the world