From this dude's home page: "Are Self-identified Bisexuals Just Lying to Us—or to Themselves?"

To be fair, if you read the posting it seems rather reasonable and its thesis doesn't match the title. Indeed, Bem is arguing against both sides of the disjunction. From the tone of the writing and the comment that it was posted online to Sexnet, I'd guess that the title comes from the discussion thread rather than from Bem himself.