First, there was the time that Kenneth was turned away from a nightclub when word got out that he was bisexual. Then, a co-worker, assuming he was gay, jeered, "I hear you're coming out of the closet."
His gay friends were just as bad. They, too, were baffled, making him feel as if something was wrong with him because he couldn't "pick a team" -- Kenneth, who did not want to use his last name for privacy reasons, was attracted to both men and women.
Now, Kenneth, a 36-year-old heating and air conditioning specialist from Orange County, Calif., is an advocate as part of the It Gets Better Campaign, and said he feels vindicated.
Just this week, the journal of Biological Psychology published a Northwestern University study that contradicted 2005 research questioning whether male bisexuality even existed. It was the second of two such papers that finds that it does.
"Bisexuality is an orientation among men, just like heterosexuality and homosexuality," said Allen Rosenthal, a doctoral student in the university's psychology department and lead author of the study.
The study included 100 men who were bisexuals, heterosexuals and homosexuals.
Researchers placed a penile plethysmograph -- a rubber band-shaped band -- on the base of men's penises while they watched videos of male to male and female to female sex.
"We measured actual physical arousal," said Rosenthal. "You can't create arousal when it isn't there for them. You can't fake it."
Kenneth says his first sexual encounter at 18 was with a man, and the relationship lasted six months. But his next two romances were with women. Today, his partner is a bisexual woman, but Kenneth said that does not diminish his attraction to men.
Bisexuals like Kenneth say that even as gays and lesbians have garnered more social acceptance, they have felt isolated.
Until now, bisexuals have been largely viewed as promiscuous or latent homosexuals, and have faced ridicule by both the gay and straight communities.
The American Institute of Bisexuality, a nonprofit organization that supports research and education, worked with Northwestern to fund part of the study to dispel those stereotypes.
"Basically, we want to respect how people define their own sexual orientation," said Denise Penn, a clinical social worker who is on the institute's board of directors.
"What you hear is this: Bisexuality is a phase for some people that they may adopt temporarily," she said. "Basically this study makes the criteria for defining yourself as a bisexual as more of a permanent thing."
Penn hailed progress in gay rights as evidenced by sympathetic characters on television sitcoms and more acceptance in the workplace.
"But if you are bisexual, it's not so simple," she said. "People define you by the person you are seen with."
Bisexuals have been perceived as "promiscuous, opportunistic, confused" even by the gay community, according to Penn. "People in persecuted minorities tend to band together with common histories and common pain. When bisexuals come into the fold, they are seen as traitors, people conferring with the enemies."
An estimated 1.8 percent of all Americans are bisexual, according to the Williams Institute of the University of California Los Angeles Law School, which focuses on lesbian, gay, bisexual and transgender issues.