Pictured: The gay style life.
Yes, it's a phrase that gets tossed around frequently in some religious and conservative circles, but "gay lifestyle" is a rice cake expression, a collection of empty syllables that convey whatever meaning the speaker supposes the audience wants to hear. Sometimes it's a gentle euphemism meant to invoke compassion for a wayward loved one, other times it's a fire-and-brimstone condemnation of the wicked. Mostly it's a signifier or shorthand for (as one LDS blogger put it) "fornication, adultery, pornography, and drug use" --the very destruction of our moral fabric.
Of course, you rarely see "gay lifestyle" precisely defined by polite religionists (and Mormons are nothing if not polite), but it carries plenty of lurid connotations -- most often that of the flamboyant, effeminate, promiscuous man with an ever-rotating caste of sexual partners, flaunting his disrespect of traditional morality. Setting aside that this stereotype hardly reflects the reality of being an average gay Joe, does that mean that the "heterosexual lifestyle" is best represented by Wilt Chamberlain?
An ambassador for the heterosexual lifestyle.
Lifestyle is also used as a code for choice, because in America we choose our lifestyle, don't we? We become wealthy by the sweat of our brow, aided by righteous living. To live a gay lifestyle is to cast aside God and live a life of decadence and sin, even if that happens to lead to plain ol' middle-class suburban monogamy (You might have gay people living next door! Horror!) Lifestyle is an implicit denial of the idea that gay people could possibly be born that way, and it's amazing how theories about absent fathers and naughty pictures still dominate the discourse about homosexuality in certain circles. There are even books sold at reputable bookstores on how to raise heterosexual kids, because it's all about teaching and making good lifestyle choices!
Not everybody goes to that extreme, but even more moderate religious people often compare homosexuality to, say, alcoholism or being short-tempered. One may be inclined toward them, but they are merely temptations -- the moral offense only comes in acting. Giving in, embracing the gay lifestyle, is a sin because it is a betrayal, not an expression, of the natural self (though oddly, nobody talks about the "alcoholic lifestyle" or the "angry lifestyle"). Unfortunately, in this view a gay person's natural self is a stranger to them until they've suffered through life alone.* Suppose you don't like fish. Now imagine being told that in the afterlife, you'll be blessed with an abundance of fishy food forever. But that doesn't sound appealing at all! Sorry friend, but the entire point of the afterlife is to raise and eat fish, and it's the only afterlife there is. If you don't like it you can starve for eternity. But don't worry -- once you get there you'll love fish, promise! Meanwhile, you don't have to eat any -- you just have to work in a fishery and help others fish all day. No problem!
When you're older you'll love this stuff
It's a silly analogy, but isn't that the exact dilemma we impose on gay people? Don't worry, the way you are isn't the way you really are, and one day you'll see your true self even if you happen to like how you already are. Even though I can parody the situation, I honestly can't imagine being in it, and I have a ton of sympathy for people who are. I respect the many people who are trying to discover or who have created a viable gay identity in their religion, LDS or otherwise. For faithful Mormons, we ought to show nothing but charity and love to gay people, just as with everybody else. We can start by not characterizing them according to fanciful notions about their "lifestyle" and worrying less about how or where they may be sinning. Maybe we'll get to a point where instead of fretting about how "overly tolerant" we might become, we can instead worry about how full of love we are.
*There are arguments that homosexuality is like any other physical handicap that prevents regular heterosexual relationships in mortality, but I don't find them convincing. Someone paralyzed from the waist-down may have more trouble finding a companion, but if they're straight they can look forward to the day when their desires will be fulfilled, which is different than saying that their actual desires will be altered.