I know plenty of straight women who have the same reaction to lesbians and bisexual women. And have had friends in the past who have admitted being bi-curious (though with no experience), and have then assumed someone in our circle who was actively Bi (but in a happily monogamous relationship at the time!) would be automatically interested in sleeping with them. Hrumph. Arrogance, pure and simple. The same blind arrogance that makes very fat girls wear crop tops and hipsters, and really ugly blokes make a beeline for the most attractive girl in any given room.