Years too late and probably will fall on deaf ears, but I was browsing over an old, amusing entry and came across this response.
Dude, fuck you. As someone who came out extremely reluctantly as a bisexual far later than in my "teen years," it's seriously attitudes like yours that contributed to my refusal to believe that I was anything but straight. Am I blaming you personally for my issues with my sexuality? Of course not. But stridently attempting to uphold our society's oppressive heteronormativity does not help make things easier for those who queer.
I didn't want to believe I was bisexual just for those very retorts you spouted: I didn't want to be seen as some trashy, slutty girl, to have people be skeptical of something I've been wrestling with painfully for most my life, to be a joke to both straight and gay people. Lord, judging by the time stamp, I faced the truth about my sexuality about a month after you posted this. At this point, I can get out the words "I am a bisexual" out loud without choking (much). But it sure was a hell of a shock at the time to realize I was part of a marginalized group where, for instance, people who have only a theoretical understanding of human sexuality can feel free to judge me and others like me as being fake and attention whores.
And even now I question whether this is just a phase and I'll go back. Even now I feel more comfortable saying that I'm gay instead of saying I'm attracted to both sexes, because I think people will accept that easier. But at least I realize those thoughts comes from this social pressure to be one sexuality or the other, and not from myself and certainly not from people who hold erroneous, archaic attitudes.