Why do people get so worked up about this issue? Why should it become the line in the sand for so many? Why should it be something that threatens to split the Anglican/Episcopal Communion, and maybe other denominations? When we Christians so evidently fail God in so many ways, such as failing in the things Jesus mentions in Matthew 25:35-36, why is this the issue that seems to produce more anger than any other?
Well, for the gay community it's obviously very personal. It's a very very hard thing to grow up gay. Feeling different, being bullied and abused in school for being a sissy. Having attractions you can't understand while everyone around you seems "normal" with girlfriends, dates, etc. Many many parents reject gay children and kick them out (hence why 50% of homeless teens are gay).
But to then have the majority of the population tell you you made a choice to be disgusting, an abomination, a spawn of Satan, mentally ill, unnatural, deviant, etc. etc., all while claiming to still "love" you, just makes the whole thing worse.
Most Christians will never know what it's like to be gay, bisexual, or transgendered, so it's an easy target to nitpick about their sins. Most of them don't understand sexual orientation anyway, so they merely think of sexual acts some gays do and pride parades, and associate that behavior with all gays. Our Macho driven society finds the idea of 2 men being affectionate to be very gross and unmanly, hence why gay men take the brunt of the stigma (straight guys find lesbians hot).
So they start with already having the prejudicial view that gays are deviant and disgusting, and then, in order to morally justify that view in the eyes of God, they take butchered scriptural verses and say "See, God hates you too!"
When we look at other sins, however, like fornication, divorce, adultery, obesity, greed, etc., Christians are by far the biggest committers of those sins, so they aren't willing to judge themselves in the mirror.
That's all it comes down. A macho society that views gay guys as gross, and since most people aren't faced with that challenge it's an easy target.