Science!

Men are more than twice as likely to continue dating a girlfriend who has cheated on them with another woman than one who has cheated with another man, according to new research from a University of Texas at Austin psychologist. Women show the opposite pattern. They are more likely to continue dating a man who has had a heterosexual affair than one who has had a homosexual affair.... "A robust jealousy mechanism is activated in men and women by different types of cues—those that threaten paternity in men and those that threaten abandonment in women," says Jaime C. Confer, the study's lead author and a doctoral candidate in evolutionary psychology.

By "men," of course, UT researchers mean "straight men who are lucky enough to have bisexual girlfriends." And by "women," of course, UT researchers mean "straight women who are unlucky enough to have bisexual boyfriends." (Please note: I wish more straight women regarded landing a bisexual boyfriend as a stroke of luck, and I encourage straight women to view a bisexual boyfriends as a great good fortune, and I encourage bisexual guys to be open about being bi and to present their bisexuality as a boon. But research—science!—tells us that most women feel otherwise. Which is too bad for straight women and the bisexual boys who date 'em and remain closeted because they feel they must.)