While it's true that there are straight women out there with "gay husbands" and "gay bffs" who treat their gay friends like little more than fun, interactive accessories and gay men out there who dismiss their straight female friends as "fag hags" (which I'll say is just as dehumanizing), the fact remains that straight women and gay men are often able to form particularly close friendships with one another. While some say that this is "fodder for future episodes of envelope-stretching comedy" (okay), it's also argued that there are more scientific and psychological explanations for it.
Psychologists have previously hypothesized that gay male/straight female friendships experience such a high success rates because of the lack of sexual attraction, the feeling of body acceptance (a 2009 found that women with gay friends reported feeling more sexually attractive and proud of their bodies than women without gay friends), a more honest rapport and a better appreciation for each others personalities. All of these studies (cited here), however, focused mainly on straight women' reasoning and not gay men's.
Now researchers at the University of Texas - Austin have theorized an evolutionary purpose to straight women/gay men friendships and how they are helpful to mating. Using a sample group of 88 heterosexual and 58 homosexual men, researchers showed their subjects the fake Facebook profile of a person named Jordan. For women, Jordan was either a straight woman, a straight man or a gay man. For the men, Jordon was either a straight woman, a gay man or a lesbian. Other than gender and sexual orientation, the profiles were identical.
Subjects were then asked to imagine being at a party with Jordan where s/he gave them romantic advice on something like "how to interpret an interaction with an attractive member of the opposite sex." They were then asked how seriously they took the advice. Both gay men and straight women perceived the advice offered by each other as being more valuable than the advice offered by their own orientation, straight men or gay women.
The psychologists claim that this is because straight women and gay men don't see each other as sexual threats or sexual competition. The team reports in Evolutionary Psychology:
Our results suggest that straight women and gay men perceive mating advice provided by each other to be more trustworthy than similar advice offered by other individuals...the emotional closeness shared by straight women and gay men may be rooted in the absence of deceptive mating motivations that frequently taint their relationships with other individuals.
Of course, these findings come off as rather clinical and removed from a person's conscious motives to be a part of a friendship. I would say that I am friends with my gay friends not for an evolutionary purpose, but for the same reasons that I'm friends with anyone — common interests and compatible personalities. (If that sounds boring, feel free to sub in "glitter, glitter and MORE GLITTER.") I'm also a tad resentful of the notion that I take my female friends' advice less seriously because I worry that they might be in sexual competition with me. In the immortal words of Lesie Knope, "Uteruses before duderuses."
Then again, maybe I'm the exception and the rest of you base all of your friendships in how they increase your chances to get laid. Somehow, I don't think that's right and that you're all better than that. Still, we should probably all discuss it with our gay husbands just to be sure.
Gay Men, Straight Women: What's the Attraction? [The Pacific Standard]