So, the good news is that there's actual evidence of bisexuality in men, as measured by physiological response to erotic stimuli. This is good news because the myth of bi men as "gay men not ready to come out" and bi women as "straight girls with a wild side" persists, and it's time to put it to rest.
(I actually did a Q and A back in Indiana with the GLBT student group on campus, and one kid said, "I think that when gays are more accepted, there won't be anyone who identifies as bisexual." To which I replied, "I think that when gays are more accepted, hardly anyone will identify as either gay or straight and most of us will just be fluid or bi- or pan- or omni-sexual.")
The irritating news is that apparently the community of bisexual men is responding to the evidence in a stupid way - at least according to the New York Times.
"It's insulting," says one guy in the NYT article. Another person says, "Researchers want to fit bi attraction into a little box -- you have to be exactly the same, attracted to men and women, and you're bisexual."
Yeah... researchers want to fit it into a box; it's not that the way to measure stuff is to standardize it. It's not that operationalizing a variable necessarily means simplifying it (anyone who has taken high school physics knows about the role of the frictionless, spherical cow). It's that researchers WANT to reduce sexual orientation to psychophysiology, they WANT clusters of homogeneous people, researchers believe that actually all people in a particular category are just alike. Yeah.
Did Kinsey have to deal with this? He pursued his interviews with the explicit goal of SHOWING THE WORLD what diversity existed. Did people say, "It's insulting that he thinks you can conclude something about sexuality just by asking a lot of people a lot of questions"?
I agree that the world shouldn't need evidence that something someone says about their internal experience - e.g., "I am turned on by people with penises and by people with vaginas," or "I feel attraction to people without reference to their gender expression" - is true. But the world is incredibly ordinary, insofar as it tends to believe that anything that isn't true about its own sexuality must either be a lie or pathology; any other conclusion is apt to make the world feel there is something wrong with ITSELF, and the world will simply not have that.
Therefore we find something plausible (if limiting and flawed) to measure - in this case, genital response - to show that, look, here are folks who get tumescent in response to boys AND girls. There are other folks who only get tumescent to one or the other, so it's important that some respond to both. And thus the world is forced to acknowledge that yes indeed, there must be bisexuals.
Because bisexuals face discrimination at least as much from gays and lesbians as from straights. They violate the simple black-and-white clarity of sexual orientation and thus threaten the importantly simple message of the gay community to the straight community: "We're just like you, only we love people with the same bodies as ourselves." Bisexuals make it seem like all bets are off, there are no rules, it's not simple.
And it's NOT simple.
But before we can talk about that productively in the public sphere, we have to agree that bisexuality EXISTS, and we need to do it in a way that people will buy. Hence psychophysiology. If we could do it affordably with fMRI and produce pretty pictures of colorful brains, we would, because people fucking LOVE that shit and they'll believe anything with a brain magnet involved.
There's an episode of "This American Life" called 81 Words about the removal of homosexuality from the Diagnostic and Statistical Manual of the American Psychiatric Association. My students listen to it when I teach about sexual orientation. Why? Because it's a story of how science interacts with social movements, and how social movements reject the science (and the scientists) trying to support their cause.
Sometimes I wonder if the dichotomy between science and political movements isn't as great as the dichotomy between science and religion.