As a teenage comic-book geek, I was captivated by John Constantine like no other character. The hard-drinking, chain-smoking punk rock occultist inhabited a grim and gritty world a million miles from the brighter, tamer settings of the Justice League and Fantastic Four. He was impossibly cynical, believably vulnerable and, like me, bisexual.

Bi male protagonists are pretty hard to come by in popular culture. That’s why it’s so disappointing – especially today as bisexual people around the world mark Celebrate Bisexuality Day – that an upcoming television adaptation of Constantine’s adventures will portray him as straight.

The show’s creators have defended their decision, arguing that since his first appearance nearly 30 years ago, Constantine has only occasionally been sexually involved with men. In doing so, they have betrayed their lack of understanding of bisexuality. They’ve assumed that to be bisexual you have to be equally attracted to men and women.

In truth, the term “bisexual” is a catch-all that covers a broad range of sexual and emotional orientations. Some people are primarily attracted to one sex, but have an occasional interest in another. Some feel purely physical attraction towards one gender, but both sexual and romantic attachment towards its counterpart. Others find that their preferences vary from time to time, and others still see the term “bisexual” itself as problematic, arguing that gender identity falls on a spectrum rather than along clearly delineated boundaries of male and female: 50-50 attraction does exist, but it isn’t the sole, definitive experience of bisexual people.

Perhaps this difficulty in nailing down bisexuality is why it’s often portrayed so poorly in the media. With the exceptions of Doctor Who’s Captain Jack Harkness and Game of Thrones’ recently departed Oberyn Martell, it’s difficult to think of many high-profile bi characters on TV or in the movies. Where bisexuals do appear, they’re often female characters used for the titillation of a straight male audience.

This allows some widely held misconceptions to go unchallenged. Too many men view bisexual women as exotic, sexually available and potentially up for a threesome. The concept of male bisexuality, on the other hand, seems to provoke a degree of disgust and denial in some people who are uncomfortable with a non-binary concept of male sexuality. As a result, bisexual characters like Constantine find themselves unceremoniously straightened.

A lack of realistic representation in fictional entertainment may seem like a minor complaint, but it’s both a result of and a contributor to popular misconceptions and anti-bi prejudice in wider society. Most bisexuals have probably been told at least once that they’re “confused” or “going through a phase”. In that case, my own confusion has lasted 23 years and shows no sign of being resolved.

We’re seen by some as a breed of sexual Typhoid Mary – held responsible for the transference of sexually transmitted infections between gay and straight communities. In reality, you’re more likely to catch an STI as a result of risky sexual practices with straight partners than you are from safe sex with a bi partner.

We’re told that we’re incapable of being faithful in relationships, same or mixed sex, because we must always secretly long for something that one partner can’t offer us. Millions of people married to bisexuals around the world, including my wife – my partner of nearly a decade – would beg to differ.

Perhaps most insulting is the accusation – propped up by deeply flawed research – that bisexuals are simply gay and lack the courage to accept and admit it. At a time when so many societies are becoming more accepting of same-sex relationships, bisexuality still carries a stigma. Yes, coming out as gay is a courageous act, but the idea that identifying as bi is some kind of copout is ridiculous.

Such erroneous beliefs have a corrosive effect. Studies have found that bisexual people suffer more mental health problems than gay and straight populations. Such information suggests that we’re also more likely to be victims of domestic violence. Bisexual asylum seekers in mixed-sex relationships face difficulty in proving their sexuality when attempting to claim refugee status, potentially resulting in their being sent back to countries where they may face violence, persecution and death.

These problems are all too real. The erasure of bisexuality from popular culture does nothing to combat them.