As we predicted, these covertly prejudiced people tended to refrain from shocking the man who was confirmed as gay, but delivered extremely high levels of shocks to the man who liked shopping. You know your gay colleague is lonely; he just I never heard of anyone refer to a haircut as gay tell you that he is lonely because he has seasonal affective disorder, or a Madame Alexander doll collection.
For example, one of my PhD students, David Harnden-Warwick, has a casual hunch that gay men may have sharper, clearer irises than straight men. For example, gay face includes tightness around the mouth from pursing the lips, a facial expression common to gay men and women—but not to heterosexual men.
Gay vagueness affects both straight and gay men. In a study on prejudice-based aggression, we had participants play a game that involved administering electric shocks to a subject in the other room. I like the Urban Dictionary because it captures people's understanding and use of words and phrases independent of their actual meaning; it's therefore as much a gauge of human psychology as it is a compendium of slang.
First, stereotyping can facilitate prejudice. What I find fascinating is that I went from bi invisibility due to my long hair and "straight" appearance to bi invisibility due to my short hair and "gay" appearance. But the very fact that it seems harmless may actually be responsible for its most pernicious effects.