Hi @Kristin2, yours is a very interesting question. By definition, guests are required to agree to your house rules before booking on IB, but if you say no single men and they book under IB anyway, that puts you in the position of having to cancel. You only have 3 penalty free cancellations per year, so that's no good. I tried to see what settings you could use for Instant Book, but the page isn't there. AGH!
My best advice to you if you get frequent reservations from people you don't want, i.e. single men, would be to turn off Instant Book.
Of course you can contact @Airbnbhelp on twitter (fastest way) or use the Contact Us link to see if there is a work around for your situation. If there is, please advise since I would like to know the answer too!