Fringe (2008): Special agent Olivia (Anna Torv) has sex with her boyfriend. He dies. She's not gay!!!!! Thank goodness! Now she can get to the business of investigating the paranormal. (See: The 12 Beefcake Stars of Fringe.)
White Collar (2009): Neal Caffrey (gay actor Matt Bomer) is visited in prison by his girlfriend. They touch hands through the glass window separating them. He's not gay!!!! Thank goodness! Now he can get to the business of investigating forgeries and frauds.
Under the Dome (2013): Every one of the 9 main characters, with the exception of the lesbian attorney, spends the first episode kissing, flirting, losing a husband/wife, or discussing a husband/wife.
Dexter (2006) was the most egregious offender, maybe because forensic scientist/serial killer Dexter was played by Michael C. Hall (below), fresh from a gay role on Six Feet Under, and it was introduced through a full-page ad in The Advocate, openly inviting gay viewers. Naturally, one assumed that it would be gay-friendly. Yet the opening scenes scream loudly, over and over, that gay people ABSOLUTELY DO NOT EXIST.
Dexter doesn't have a girlfriend, but they find other ways to proclaim universal heterosexuality:
1. He goes to a crime scene, where one of the investigators exclaims that his sister is hot and the other commentss on the dismembered woman's attractiveness.
2. He goes to the police station, inquires about the hetero-romances of his coworkers, and talks to an older women, who advises "You should find a pretty girl,” utterly unaware that some men are gay.
4. Dexter announces that he doesn't experience emotion, and doesn't care for sex, although he "appreciates women, like every man."
5. However, in order to keep up an "appearance of normalcy," he is dating a woman.
Why go through the trouble of advertising a television program to an audience, and then devote the entire first episode to chanting "You don't exist! Ha-ha!"