Looks like it's time once again for a reminder of the lines from the Bisexual Manifesto, back in 1990:
"Do not assume that bisexuality is binary or duogamous in nature: that we have "two" sides or that we must be involved simultaneously with both genders to be fulfilled human beings. In fact, don't assume that there are only two genders."
https://web.archive.org/web/20051026101614/http://www.anythingthatmoves.com/manifesto.html, ¶5 (2nd graf after big, bold, centered one)