The only true bisexuals are people who are equally attracted to both sexes. Bisexuals can't form stable relationships. Name calling Bisexuals are have no moral values. Bisexuals are immature. Bisexuals are unreliable.
Bisexuality is a political cop-out.
The ways people can experience sexuality form a multi-dimensional continuum. Different people would draw their erotic potential as regions of different shapes on such a map. Over time, some people change, uncovering new areas or shifting in emphasis. This raises political questions. There are no sharp lines around these regions of experience.