Two Kinds Of Christian Homophobia
It seems to me, though, that Christian homophobia is being defined too narrowly here. It's easy to see how the foaming-at-the-mouth crowd is homophobic, because they're always talking about same-sex sex. What gets ignored is the homophobia-by-omission that characterizes much of Christianity.
Slacktivist's background is in "evangelical" churches (Southern Baptist, IIRC), so it's natural that he'd focus on the Falwellians. But my church-going experience is quite different. I've spent a lot of time in "mainline" churches, mostly ELCA. (Despite the name, the Evangelical Lutheran Church in America is not "evangelical" in the way we usually use that term to describe a subset of Christianity.) In all the sermons I've listened to growing up, and peripheral literature I've seen, I cannot recall a single mention of homosexuality*. I arrived at college with only the barest conception that there were people out there who were attracted to members of the same sex.
It would be easy to point to churches like the one I attended as evidence that Christianity is not anti-gay. To do that, though, is to conflate homophobia in general with the particular form of overt homophobia practiced by Falwell et al. That would be an error similar to the way white liberals assume that anyone who's not wearing a white hood or endorsing racial IQ disparities is not racist. But in fact you can be homophobic** without directing active hatred toward non-heterosexuals.
The churches I've attended can be described as "unreflexively heteronormative." The Falwellian strain of homophobia recognizes homosexuality as an alternative way of life in opposition to the conservative Christian one -- Fred Phelps has to highlight homosexuality and describe its contours (in whatever twisted way) in order to actively attack it. Unreflexive heteronormativity, on the other hand, represses homosexuality by failing to acknowledge its existence. I'm not saying that the people at the churches I've gone to don't know about the existence of LGBTs. What I'm saying is that that knowledge is detached from everything else in their lives. If nobody is specifically raising it as an issue, they go about the life of the church on the assumption that everyone is heterosexual (and, to a lesser degree, that they come from and desire to start a "normal" nuclear family). Accommodation for LGBTs has to be created by carving out exceptions on a case-by-case basis, and will only be done when a person specifically raises the issue.
I'm not interested in debating which type of homophobia is how much worse than the other (though this post would be a lot more powerful if I were LGBT and could describe the particular pains of growing up in an environment that, instead of actively attacking me, simply failed to acknowledge that I and my struggles existed). The point is that homophobia comes in more than one flavor, and over-focusing on the Falwellian typw can lead to ignoring the need to address unreflexive heteronormativity (both inside and outside Christianity***).
*This was my experience in the Boy Scouts as well. Much of my analysis of the two forms of homophobia in Christianity could doubtless apply to the Scouts as well.
**I describe people as "homophobic" and "racist" for convenience here, though in engaging with such individuals I would be more likely to describe them as "doing things that perpetuate oppression on the basis of sexuality/race." The longer phrasing is better because it doesn't imply any presuppositions about the person's motivations, and because it keeps the focus where it belongs -- on the effects of one's actions on LGBTs or POC, not on the purity of one's soul.
***The fact that Falwellian homophobia is so closely linked to one sect of Christianity while unreflexive heteronormativity crosses religious lines may be part of the explanation for why it gets so much attention -- it's a lot easier to identify an attack an overtly hostile Them than to do the therapeutic work of overturning more widespread harmful assumptions.